Ideological Reversal among Supreme Court Justices

The purpose of this paper is to assess ideological change of Supreme Court justices from 1937 to 2015. Using Martin-Quinn scores, we find that for most four-year presidential terms, Democratic president Court appointees are more liberal and Republican president appointees are more conservative. Yet among justices with a minimum tenure of seven years, simple bilinear regression on a time trend variable shows that ten of eighteen justices appointed by Republican presidents have drifted to the left, while seven of sixteen justices appointed by Democratic presidents have drifted to the right. We conclude that ideological drift among justices, especially in a direction contrary to what the appointing president might have predicted, appears to be more common than exceptional.

• Supreme Court Justices
• Martin-Quinn Scores
• Regression

1. Introduction

The recent confirmation of Neil Gorsuch to the U.S. Supreme Court (April 7, 2017) following a 14-month vacancy created after the death of Justice Antonin Scalia begs the question: How many more opportunities will President Donald Trump have to appoint another justice to the Supreme Court? Article II, Section 2, Clause 2 of the U.S. Constitution gives the president the pro forma power to nominate judges to the Supreme Court. However, given the lifetime tenure of Supreme Court justices, it is difficult to predict when a president will be presented with a Court vacancy. After all, an appointment to the Supreme Court can only occur after a sitting justice dies, resigns, or retires. Five current justices (as of July 1, 2017) are older than 65 years of age―Samuel Alito (67), Clarence Thomas (69), Stephen Breyer (78), Anthony Kennedy (80), and Ruth Bader Ginsburg (84). Thus, the remainder of President Donald Trump’s term could resemble that of Presidents William H. Harrison, Zachary Taylor, Andrew Johnson, and Jimmy Carter―all of whom made no appointments at all to the highest judicial body in the land―or his remaining time in office might more closely resemble that of the six presidents who successfully appointed five or more members to the Court (Gunther [1] , Appendix B).¹ Nevertheless, the power of appointment is by no means absolute, as the president requires the consent of (that is, a simple majority vote in) the Senate.

We examine the extent of political harmony between presidents and their successful appointees. One would expect that Republican presidents would appoint conservative justices and Democratic presidents would appoint liberals. Presidents nominate kindred spirits who will, they hope, hold the same ideology for as long as they serve on the Court. But, does the judicial ideology of Supreme Court justices change over time? Is ideological drift among Supreme Court justices likely even in the absence of membership turnover? Do justices appointed by Democratic (Republican) presidents become more liberal (conservative)? Or, is there often a reversal in ideology during their tenure on the Court?

In this paper, we use Martin-Quinn (hereafter abbreviated M-Q) measures of judicial ideology to compare M-Q averages between Republican- and Democratic-appointed justices, and to determine whether M-Q justice-specific scores change over time.

2. The Data

Martin and Quinn [2] estimated ideological scores for every Supreme Court justice for every term between October 1937 (during Franklin D. Roosevelt’s second presidential term) and October 2015 (during Barack Obama’s second term). A negative M-Q score reflects liberal ideology whereas a positive M-Q score reflects a conservative ideology. In general, higher values represent greater conservatism. The updated M-Q scores through 2015 can be found at [3] . The data set includes M-Q scores (referred to by Martin and Quinn as the justice’s “posterior mean”) for 22 different Democratic appointees who collectively served a total of 321 years (mean: −1.0216, standard deviation: 2.0898) and 23 Republican appointees who collectively served a total of 398 years (mean: 0.7074, standard deviation: 1.8435). For all 45 Supreme Court justices, Table 1 shows their mean M-Q score over the time they served on the Supreme Court, the start and ending dates of their tenure, the length of their tenure (in days), and the name and party affiliation of the president who appointed them.²

Table 2 shows the top five most liberal (largest negative M-Q score) and most conservative (largest positive M-Q score) justices classified by the political party of the appointing president. Harry S. Truman appointed four justices during his

Table 1

Martin-Quinn Scores of Supreme Court Justices, 1937-2015

Justice	Martin-Quinn Scorea	Tenure		Days	Appointed by
		Start	End
James C. McReynolds Louis Brandeis George Sutherland Pierce Butler Harlan F. Stone Charles E. Hughes Owen J. Roberts Benjamin N. Cardozo Hugo Black Stanley F. Reed Felix Frankfurter William O. Douglas Frank Murphy James F. Byrnes Robert H. Jackson Wiley B. Rutledge Harold H. Burton Fred M. Vinson Tom C. Clark Sherman Minton Earl Warren John M. Harlan II William J. Brennan Charles E. Whittaker Potter Stewart Byron White Arthur Goldberg Abe Fortas Thurgood Marshall Warren E. Burger Harry Blackmun Lewis F. Powell William Rehnquist John P. Stevens Sandra D. O’Connor Antonin Scalia Anthony Kennedy David Souter Clarence Thomas Ruth B. Ginsburg Stephen Breyer John Roberts Samuel Alito Sonia Sotomayor Elena Kagan	3.46925 −0.61750 1.57400 2.22050 0.01367 0.17925 1.53338 −1.59800 −1.75868 0.37845 0.49954 −4.64892 −1.58740 −0.19000 0.69769 −1.41543 1.04464 1.04643 0.50367 1.12325 −1.25781 1.62453 −1.93403 1.23533 0.43752 0.42313 −1.05367 −1.43500 −2.81267 1.86065 −0.03036 0.94206 2.94803 −1.82100 0.98084 2.46753 0.69724 −0.78668 3.52348 −1.54504 −1.13214 1.11064 1.66036 −2.04200 −1.52967	Aug. 29, 1914 Jun. 1, 1916 Sep. 5, 1922 Dec. 21, 1922 Feb. 5, 1925 Oct. 10, 1910 Feb. 24, 1930 May 20, 1930 Mar. 2, 1932 Aug. 18, 1937 Jan. 27, 1938 Jan. 20, 1939 Apr. 15, 1939 Jan. 18, 1940 Jul. 8, 1941 Jul. 11, 1941 Feb. 11, 1943 Sep. 22, 1945 Jun. 24, 1946 Aug. 19, 1949 Oct. 12, 1949 Oct. 5, 1953 Mar. 17, 1955 Oct. 15, 1956 Mar. 22, 1957 Oct. 14, 1958 Apr. 16, 1962 Sep. 28, 1962 Oct. 4, 1965 Oct. 2, 1967 Jun. 23, 1969 Jun. 9, 1970 Jan. 7, 1972 Jan. 7, 1972 Dec. 19, 1975 Sep. 25, 1981 Sep. 26, 1986 Feb. 18, 1988 Oct. 9, 1990 Oct. 23, 1991 Aug. 10, 1943 Aug. 3, 1994 Sep. 29, 2005 Jan. 31, 2006 Aug. 8, 2009 Aug. 7, 2010	Jan. 31, 1941 Feb. 13, 1939 Jan. 17, 1938 Nov. 16, 1939 Apr. 22, 1946 Jun. 10, 1916 Jun. 30, 1941 Jul. 31, 1945 Jul. 9, 1938 Sep. 17, 1971 Feb. 25, 1957 Aug. 28, 1962 Nov. 12, 1975 Jul. 19, 1949 Oct. 3, 1942 Oct. 9, 1954 Sep. 10, 1949 Oct. 13, 1958 Sep. 8, 1953 Jun. 12, 1967 Oct. 15, 1956 Jun. 23, 1969 Sep. 23, 1971 Jul. 20, 1990 Mar. 31, 1962 Jul. 3, 1981 Jun. 28, 1993 Jul. 26, 1965 May 14, 1969 Oct. 1, 1991 Sep. 26, 1986 Aug. 3, 1994 Jun. 26, 1987 Sep. 3, 2005 Jun. 29, 2010 Jan. 31, 2006 Feb. 13, 2016 Jun. 29, 2009	9653 8293 5614 6175 7748 2071 4145 5552 2321 12,449 6970 8622 13,361 3471 453 4839 2404 4770 2604 6507 2561 5741 6035 12,332 1836 8299 11,397 1033 1319 8766 6305 8822 5650 12,295 12,612 8895 10,733 10,697c 6839 9354c 8697c 8339c 4264c 4140c 2855c 2491c	Woodrow Wilson (D) Woodrow Wilson (D) Warren G. Harding (R) Warren G. Harding (R) Calvin Coolidge (R) William H. Taft (R) Herbert Hoover (R) Herbert Hoover (R) Herbert Hoover (R) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) Harry S. Truman (D) Harry S. Truman (D) Harry S. Truman (D) Harry S. Truman (D) Dwight D. Eisenhower (R) Dwight D. Eisenhower (R) Dwight D. Eisenhower (R) Dwight D. Eisenhower (R) Dwight D. Eisenhower (R) John F. Kennedy (D) John F. Kennedy (D) Lyndon B. Johnson (D) Lyndon B. Johnson (D) Richard M. Nixon (R) Richard M. Nixon (R) Richard M. Nixon (R) Richard M. Nixon (R)b Gerald Ford (R) Ronald W. Reagan (R) Ronald W. Reagan (R) Ronald W. Reagan (R) George H. W. Bush (R) George H. W. Bush (R) Bill Clinton (D) Bill Clinton (D) George W. Bush (R) George W. Bush (R) Barack Obama (D) Barack Obama (D)

Source: All Martin-Quinn scores are from the 2015 Supreme Court justice data file at http://mqscores.berkeley.edu/measures.php. We used the posterior mean score to represent the “ideal point” estimate of each justice each term (or year). ^aMartin-Quinn scores are based on terms of service since 1937. ^bWilliam Rehnquist began his tenure as chief justice (appointed by Ronald Reagan) on September 26, 1986. ^cAll figures are as of June 1, 2017.

Table 2

Five Most Liberal and Conservative Justices Appointed by Democratic and Republican Party Presidents

Five most liberal justices appointed by a Democratic Party president
William O. Douglas (M-Q score: −4.649; appointed by F. D. Roosevelt) Thurgood Marshall (−2.813; Lyndon B. Johnson) Sonia Sotomayor (−2.042; Barack Obama) Hugo Black (−1.759; F. D. Roosevelt) Frank Murphy (−1.587; F. D. Roosevelt)
Five most conservative justices appointed by a Democratic Party president
James C. McReynolds (3.469; Woodrow Wilson) Sherman Minton (1.123; Harry S. Truman) Fred M. Vinson (1.046; Harry S. Truman) Harold H. Burton (1.045; Harry S. Truman) Robert H. Jackson (0.698; F. D. Roosevelt)
Five most liberal justices appointed by a Republican Party president
William J. Brennan (−1.934; Dwight D. Eisenhower) John P. Stevens (−1.821; Gerald Ford) Benjamin N. Cardozo (−1.598; Herbert Hoover) Earl Warren (−1.258; Dwight D. Eisenhower) David H. Souter (−0.787; George H. W. Bush)
Five most conservative justices appointed by a Republican Party president
Clarence Thomas (3.523; George H. W. Bush) William Rehnquist (2.948; Richard M. Nixon) Antonin Scalia (2.468; Ronald W. Reagan) Pierce Butler (2.221; Warren G. Harding) Warren E. Burger (1.861; Richard M. Nixon)

Source: Annual scores are from http://mqscores.berkeley.edu/measures.php. Mean scores are based on the length of the justice’s career.

time in the Oval Office (between April 12, 1945 and January 20, 1953), three of whom are among the five most conservative justices appointed by a sitting Democratic president since October 1937. By comparison, of the five justices appointed by Dwight D. Eisenhower during his two terms (between January 20, 1953 and January 20, 1961), two are among the five most liberal justices appointed by a Republican president in our sample. Richard M. Nixon was most successful among Republicans stacking the Court with conservatives, while Franklin D. Roosevelt was most successful among Democrats stacking the Court with liberals.

3. Methodology

Two modes of statistical analysis―t-tests and simple regression―are employed to assess ideological drift among Supreme Court justices since October 1937.

First, we ran a series of one-tailed two-sample t-tests on the difference between average M-Q scores of appointees of each political party in each of the 20 four-year administrations since 1937. The null hypothesis (H₀) is stated as follows:

H 0 : μ Democratic = μ Republican (1)

while the one-tailed competing alternative hypothesis (H_A) is:

H A : μ Democratic < μ Republican (2)

where μ denotes the average M-Q score of all justices (appointed by a Democratic or a Republican president) for each presidential term. Rejecting H₀ in favor of H_A would suggest that the justices appointed by a Democratic president were markedly more liberal than their Republican counterparts on the Supreme Court during that administration.

Finally, for each of the 34 justices with a minimum of seven years of service, we used STATA to regress the justice’s annual M - Q score against Year (a time trend variable), as follows:

M - Q score = b 0 + b 1 Year (3)

A positive and statistically significant value for b₁ would suggest that the justice became more conservative over time. Similarly, a negative and statistically significant value for b₁ would suggest that the justice became more liberal.³

4. Presentation of the Results

Table 3 summarizes the results of the two-sample t-tests which compare the average M-Q scores of Democratic and Republican appointees for each administration since 1937. During Truman’s administration (following his election in 1948), all nine justices had been appointed by Democratic presidents, but surprisingly their average M-Q score (0.4592) was positive and statistically discernible from zero (p = 0.011). That is, the F. D. Roosevelt appointees (R.H. Jackson, Reed, Black, Frankfurter, Douglas) and Truman appointees (Vinson, Minton, Burton, Clark) were as a group conservative. Moreover, the difference between the average M-Q score of Democratic appointees and that of Republican appointees was not statistically discernible in Eisenhower’s 1^st term (1953-1956, p = 0.3445) and Clinton’s 1^st term (1993-1996, p = 0.0574). However, in all other administrations, justices who were Democratic appointees rendered more liberal decisions (i.e., their average M-Q scores were significantly lower) than their Republican-appointed counterparts. And, these differences were most pronounced during Roosevelt’s third term in office and Obama’s two terms in office.

The regression results in Table 4 indicate a significant ideological drift (i.e., p < 0.05 on the estimated slope coefficient) for 27 of the 34 justices with a minimum of seven years on the Supreme Court.

Nine (two Republican appointees, seven Democratic appointees) became more conservative and eighteen (ten Republican appointees, eight Democratic appointees) became more liberal. In all twenty-seven regressions, the simple linear model fits quite well (with R², a measure of the explanatory power of the regression, 0.70 or higher for twenty of the justice-specific regressions).

Table 5 highlights the ideological drift among Supreme Court justices. Among Republican presidents, Nixon appointees (Burger, Blackmun, Rehnquist) and two appointees each by Eisenhower (Warren, Brennan), Reagan (O’Connor, Kennedy), and George H. W. Bush (Souter, Roberts) became more liberal. Only one of Coolidge’s appointees (Stone) and Hoover’s appointees (O.J. Roberts) became more conservative. Among Democratic presidents, four of Roosevelt’s appointees (Black, Reed, Frankfurter, Jackson) and two of Truman’s appointees (Burton, Vinson) became more conservative. Two appointees each by Roosevelt (Douglas, Rutledge), Truman (Clark, Minton), and Clinton (Ginsburg, Breyer) became more liberal. The trend toward conservatism (Black, Reed, Frankfurter) and that toward liberalism (Clark, Warren, Blackmun) are in general agreement with results obtained by Martin and Quinn [4] and Epstein et al.

Table 3

Average Martin-Quinn Scores of Supreme Court Justices, 1937-2015, by Administration and Party of the President

Administration	Years	Combined justice-years Justice appointed by		Average Martin-Quinn Score		p-value on difference between meansa
		Republican (R)	Democrat (D)	R	D
F.D. Roosevelt (2nd) F.D. Roosevelt (3rd) Roosevelt/Truman Truman Eisenhower (1st) Eisenhower (2nd) Kennedy/Johnson Johnson Nixon (1st) Nixon/Ford Carter Reagan (1st) Reagan (2nd) G.H.W. Bush Clinton (1st) Clinton (2nd) G.W. Bush (1st) G.W. Bush (2nd) Obama (1st) Obama (2nd)c	1937-1940 1941-1944 1945-1948 1949-1952 1953-1956 1957-1960 1961-1964 1965-1968 1969-1972 1973-1976 1977-1980 1981-1984 1985-1988 1989-1992 1993-1996 1997-2000 2001-2004 2005-2008 2009-2012 2013-2015	16b 8 1 0 9 19 17 16 22 26 28 28 28 30 29 28 28 29 21 15	22 28 35 36 29 18 20 20 14 11 8 8 8 6 7 8 8 8 15 12	0.3638 1.3723 0.7260 - 0.0893 0.2178 0.1539 −0.1171 1.0815 1.0211 0.5892 0.6977 0.3519 0.6161 0.8723 0.9478 0.6692 0.7398 1.5363 1.2903	−0.8934 −1.0639 −0.3710 0.4592 −0.1672 −1.0821 −1.6429 −1.8710 −2.2881 −2.5604 −1.5265 −1.5626 −1.5665 −1.0128 −0.4519 −1.0161 −1.4764 −1.4806 −1.6849 −1.9744	0.0264 <0.0001 - - 0.3445 0.0364 0.0084 0.0129 0.0001 0.0002 0.0058 0.0053 0.0197 0.0349 0.0574 0.0115 0.0057 0.0028 <0.0001 <0.0001

^aThe two competing hypotheses are: H₀: diff = mean(D) − mean(R) = 0 and H_A: diff < 0; ^bSix justices were appointed by a Republican president and served a combined total of 16 years between 1937 and 1940 [Pierce Butler (2), Benjamin N. Cardozo (1), Charles E. Hughes (4), Owen J. Roberts (4), Harlan F. Stone (4), and George Sutherland (1)]. ^cObama’s second term through 2015.

Table 4

Summary of Regression Results, Justices with a Minimum of Seven Years of Service since 1937

Justice	Appointed by	Constant (b0)	Slope (b1)	R2	Terms
H. F. Stone O. J. Roberts H. Black S. F. Reed F. Frankfurter W. O. Douglas F. Murphy R. H. Jackson W. B. Rutledge H. H. Burton F. M. Vinson T. C. Clark S. Minton E. Warren J. Harlan II W. J. Brennan P. Stewart B. R. White T. Marshall W. E. Burger H. Blackmun L. Powell W. Rehnquist J. P. Stevens S. D. O’Connor A. Scalia A. Kennedyb D. Souter C. Thomasb R. B. Ginsburgb S. Breyerb J. Robertsb S. Alitob S. Sotomayorb	Coolidge (R) Hoover (R) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) F. D. Roosevelt (D) Truman (D) Truman (D) Truman (D) Truman (D) Eisenhower (R) Eisenhower (R) Eisenhower (R) Eisenhower (R) Kennedy (D) L. B. Johnson (D) Nixon (R) Nixon (R) Nixon (R) Reagan, Nixon (R) Ford (R) Reagan (R) Reagan (R) Reagan (R) G. H. W. Bush (R) G. H. W. Bush (R) Clinton (D) Clinton (D) G. W. Bush (R) G. W. Bush (R) Obama (D)	−395.400 (−6.93)1* −777.092 (−14.18)* −169.810 (−9.67)* −273.801 (−10.58)* −173.504 (−5.71)* 368.394 (12.92)* 2.889 (0.10) −124.852 (−2.81)*** 241.918 (5.12)* −105.241 (−5.04)* −391.190 (−9.25)* 119.832 (4.42)* 191.771 (4.29)** 89.320 (2.14)*** 11.396 (0.17) 186.074 (16.85)* 7.535 (0.59) −67.166 (−5.65)* 349.587 (18.51)* 77.752 (2.49)*** 292.949 (25.97)* 43.599 (1.84) 229.340 (16.27)* 218.245 (11.02)* 128.824 (11.74)* 33.531 (1.21) 93.903 (10.12)* 274.693 (10.96)* 23.158 (1.21) 189.698 (13.35)* 88.448 (7.23)* 219.360 (5.46)* −15.187 (−0.33) 370.537 (10.08)*	0.204 (6.93)* 0.401 (14.21)* 0.086 (9.57)* 0.141 (10.60)* 0.089 (5.72)* −0.191 (−13.08)* −0.002 (−0.16) 0.065 (2.83)*** −0.125 (−5.15)* 0.055 (5.10)* 0.201 (9.28)* −0.061 (−4.40)* −0.098 (−4.27)** −0.046 (−2.17)*** −0.005 (−0.15) −0.095 (−17.03)* −0.004 (−0.55) 0.034 (5.69)* −0.178 (−18.66)* −0.038 (−2.43)*** −0.148 (−25.98)* −0.022 (−1.80) −0.114 (−16.06)* −0.111 (−11.11)* −0.064 (−11.65)* −0.016 (−1.12) −0.047 (−10.05)* −0.138 (−10.99)* −0.010 (−1.02) −0.095 (−13.46)* −0.045 (−7.32)* −0.109 (−5.43)* 0.008 (0.36) −0.185 (−10.14)*	0.873 0.971 0.741 0.862 0.598 0.826 0.003 0.421 0.841 0.684 0.945 0.548 0.752 0.253 0.001 0.901 0.014 0.519 0.941 0.282 0.967 0.187 0.890 0.789 0.855 0.043 0.789 0.877 0.044 0.896 0.728 0.766 0.015 0.954	9a 8a 34 20 24 38 10 13 7 14 7 18 8 16 17 34 23 32 24 17 25 16 34 35 25 30 29 19 25 23 22 11 11 7

¹Numbers in parentheses are t-values. ^aIncludes only terms since 1937. ^bIncumbent as of June 1, 2017. *p < 0.001; **p < 0.01; ***p < 0.05.

Table 5

Evolution of Justices’ Decisions, 1937-2015 a .

Justices appointed by Republican presidents (18) More conservative (2) H. F. Stone (1925-1946) [Coolidge] O. J. Roberts (1930-1945) [Hoover] More liberal (10) E. Warren (1953-1969) [Eisenhower] W. J. Brennan (1956-1990) [Eisenhower] W. E. Burger (1969-1986) [Nixon] H. Blackmun (1970-1994) [Nixon] W. Rehnquist (1972-2005) [Nixon] J. P. Stevens (1975-2010) [Ford] S. D. O’Connor (1981-2006) [Reagan] A. M. Kennedy (1988-) [Reagan] D. Souter (1990-2009) [G. H. W. Bush] J. Roberts (2005-) [G. H. W. Bush] No change (6) J. Harlan II (1955-1971) [Eisenhower] P. Stewart (1958-1981) [Eisenhower] L. Powell (1972-1987) [Nixon] A. Scalia (1986-2016) [Reagan] C. Thomas (1991-) [G. H. W. Bush] S. Alito (2006-) [G. H. W. Bush]

Justices appointed by Democratic presidents (16) More conservative (7) H. Black (1937-1971) [F. D. Roosevelt] S. F. Reed (1938-1957) [F. D. Roosevelt] F. Frankfurter (1939-1962) [F. D. Roosevelt] R. H. Jackson (1941-1954) [F. D. Roosevelt] H. H. Burton (1945-1958) [Truman] F. M. Vinson (1946-1953) [Truman] B. R. White (1962-1993) [Kennedy] More liberal (8) W. O. Douglas (1939-1975) [F. D. Roosevelt] W. B. Rutledge (1943-1949) [F. D. Roosevelt] T. C. Clark (1949-1967) [Truman] S. Minton (1949-1956) [Truman] T. Marshall (1967-1991) [L. B. Johnson] R. B. Ginsburg (1993-) [Clinton] S. G. Breyer (1994-) [Clinton] S. Sotomayor (2009-) [Obama] No change (1) F. Murphy (1940-1949) [F. D. Roosevelt]

^aJustices with a minimum of seven years of service since 1937.

Potter Stewart (1958-1981), an Eisenhower appointee, demonstrated no significant change in ideology during his tenure on the Court. But, his M-Q score relative to the Court average varied from year to year, ranging from a z-value as low as 0.025 to as high as 0.645.⁴ Hugo Black (1937-1971), a F. D. Roosevelt appointee who became more conservative during his tenure on the Court, had z-values as low as −1.704 (in 1960) and as high as 0.546 (in 1968). Harry Blackmun (1970-1994), a Nixon appointee who became more liberal during his tenure, had z-values as low as −1.305 (in 1992) and as high as 0.770 (in 1970). These three justices underscore an area for future research that employs z-values to assess ideological shift. Another question we leave for further research is: Does a justice-specific z-value vary with the party of the president in office? That suggests that a Democratic appointee may be more conservative relative to the rest of the Court (that is, his or her z-value will be higher) when a Republican occupies the Oval Office.

5. Concluding Remarks

President Truman once remarked: “Whenever you put a man on the Supreme Court, he ceases to be your friend.” Due to the lifetime tenure of Supreme Court justices, it is difficult to predict ideological change throughout their respective terms.

Using Martin-Quinn scores on Supreme Court justices, the results presented here show that the party which controls the White House obviously makes a difference: Democrats appoint liberal justices and Republicans appoint conservatives. The main contribution of this research is that there is not only ideological drift among these justices, but in many instances ideological reversal. Simple regression models show that the degree of ideological reversal among Supreme Court justices appointed since 1937 has been remarkable. Ten of the eighteen justices appointed by Republican presidents became more liberal and seven of the sixteen justices appointed by Democratic presidents became more conservative. In other words, the ideologies of half of the Supreme Court justices (with a minimum of seven years of service since 1937) reversed direction. The chance that President Trump’s appointee (or future appointees) to the Court will remain faithful to conservative values may not be better than a coin toss.

With the recent addition of Neil Gorsuch to the Supreme Court, five of the current nine justices are Republican president appointees. The practical social significance of our findings lies partially in the fate of President Trump’s “travel ban” and other forthcoming Court cases. Their outcomes may disappoint today’s conservative leadership in the two other branches of government. Of equal relevance are rumors of centrist Anthony Kennedy’s impending retirement, which in the present administration could move the Court decisively to the right. Yet, the frequency of ideological reversal may frustrate Republican efforts to secure a lastingly conservative Supreme Court.

References

1. Gunther, G. (1985) Constitutional Law. 11th Edition, The Foundation Press, Mineola, New York.

2. Martin, A.D. and Quinn, K.M. (2002) Dynamic Ideal Point Estimation via Markov Chain Monte Carlo for the U.S. Supreme Court 1953-1999. Political Analysis, 10, 134-153. https://doi.org/10.1093/pan/10.2.134

3. Martin-Quinn Scores, N.p. http://mqscores.berkeley.edu/measures.php

4. Martin, A.D. and Quinn, K.M. (2007) Assessing Preference Change on the U.S. Supreme Court. The Journal of Law, Economics, and Organization, 23, 303-325. https://doi.org/10.1093/jleo/ewm028

5. Epstein, L., Martin, A.D., Quinn, K.M. and Segal, J.A. (2007) Ideological Drift among Supreme Court Justices: Who, When, and How Important? Northwestern University Law Review, 101, 1483-1541. http://scholarship.law.berkeley.edu/facpubs/1999