Notes on A Case for Supreme Court Term Limits? — Sharma & Glennon (2013)

The Case for Supreme Court Term Limits? — Study Notes

The Research Question and Core Claim

• Central question: How does the ideological relationship between appointing presidents and Supreme Court justices change as justices accumulate terms on the Court?
• Main finding (abstract and conclusions): Justices drift away from the appointing president’s ideology with each additional term served; ideological convergence between appointing presidents and justices weakens over time. The onset of significant drift occurs near the later part of a justice’s tenure (beginning around the 11th term; Table 2 provides term-by-term evidence). This has implications for debates about Supreme Court term limits from a democratic theory perspective.
• Context: The debate over judicial independence versus democratic accountability in life-tenured courts; exploration of whether term limits might preserve democratic principles without destroying independence.

Theoretical Frameworks Used

• Acclimation effect (freshman effect): Justices’ voting behavior may differ in early terms versus later terms as they acclimate to the Court. Classic work identifies variability in early terms, but without a standardized acclimation window.
  • Prior work highlights two approaches to acclimation: writing opinions and voting directions; this study emphasizes voting behavior relative to the appointing president’s ideology.
  • Hurwitz and Stefko (2004) define acclimation as a dynamic process, breaking time into blocks; Sharma & Glennon adopt a year-by-year time-series approach to capture term-by-term drift.
• New Institutionalism: Emphasizes interaction among the judiciary and other branches; aims to explain how and why justices may mirror appointing presidents early on and drift toward independence later.
  • Rationale: Post-confirmation interaction with executive and legislative branches, information flows (e.g., solicitor general), and political capital influence initial congruence with appointing presidents.
  • Prior work shows congruence may be higher early in a justice’s career, especially under unified government; later drift toward independent voting is expected.
• Combined approach: The study blends acclimation theory with new institutionalism to explain term-by-term drift, controlling for broader political climate shifts.

Data and Measurement Overview

• Core data source: Judicial Common Space (JCS) scores, aligned on a common ideological plane with presidential scores (via rescaled Martin–Quinn scores to be compatible with DW-NOMINATE Common Space scores).
• Time frame and sample: 1937–2007 Court terms; 35 justices; panel dataset covers 611 justice-term observations (Table 1 reference).
• Dependent variable: Justice Drift Score (JDS)
  • Definition: The yearly distance between a justice’s Judicial Common Space score and the appointing president’s Common Space score for the same term.
  • Calculation detail: JCS scores used are the first-dimension scores; drift is computed for each justice-term.
  • Descriptive: JDS has a mean of approximately 0.352 and a range from 0 to about 1.17 (higher means more drift).
  • Directionality: To capture directional drift, the study assigns a drift value of 0 for cases where the drift would move toward the appointing president’s ideology (e.g., Republican appointees more conservative than the president, or Democratic appointees more liberal than the president). The primary analysis uses the absolute drift but Table 2 analyzes effects in intervals to detect when drift becomes statistically meaningful.
• Primary independent variable: Terms Served by Justice
  • Treated as a continuous variable ranging from 1 to 37 terms; mean around 12.15 terms.
  • Rationale: Enables precise estimation of how drift evolves with each additional term rather than imposing arbitrary period cutoffs.
• Major controls (non-institutional and institutional):
  • Non-institutional (confirmation-related) controls
  • Appointing President’s Approval Rating at the time of confirmation vote (Gallup, via Roper Center data; mean ~58%, range 38–83%). Rationale: Higher approval could reflect political capital to appoint ideologically closer nominees.
  • Appointing President’s Distance to Filibuster Pivot: Absolute distance between the appointing president’s Common Space score and the pivot senator’s score at the time of confirmation (filibuster pivot). Rationale: Closer ideological distance to pivot reduces opposition risk and may influence confirmation dynamics.
  • Years Served as Federal Judge before Supreme Court confirmation: Continuous (mean ~3.12; range 0–16). Rationale: Prior judicial experience may signal predictable ideological tendencies to the appointing president.
  • Institutional controls (postconfirmation political environment)
  • Congressional Drift: Absolute difference between median Congressional ideology at confirmation and at the time of a decision.
  • Presidential Drift: Absolute difference between the sitting president’s ideology at decision time and the appointing president’s ideology (0 while the appointing president is in office).
  • Court Median Drift: Absolute difference between Supreme Court median ideology at appointment and at decision time.
• Data handling notes:
  • The analysis uses Generalized Least Squares (GLS) with a random-effects time-series structure to account for across-justice heterogeneity and temporal dynamics.
  • Robust standard errors are used to address heteroskedasticity.
  • Multicollinearity checks show Variance Inflation Factor (mean VIF) around 3.63; no severe multicollinearity detected.
  • The model uses a randomly varying justice-specific effect (ui) and a time component (εit).

Formal Model (Key Equation)

• The core specification (GLS random-effects time-series) is expressed as follows for each justice i in term t:

Y{it} = eta0 + eta1 ext{TermsServed}{it} + eta2 ext{CongressionalDrift}{t} + eta3 ext{PresidentialDrift}{t} + eta4 ext{CourtMedianDrift}{t} + eta5 ext{AppointingPresDistanceToFilibusterPivot}{t} + eta6 ext{AppointingPresApproval}{t} + eta7 ext{YearsAsFederalJudge}{it} + ui + u{it}

• Where:
  • $Y_{it}$ = Justice Drift Score (absolute distance between the justice’s JCS and appointing president’s JCS for term t).
  • $ ext{TermsServed}_{it}$ = Years/Terms served by justice i up to term t (continuous 1–37).
  • $ ext{CongressionalDrift}{t}$, $ ext{PresidentialDrift}{t}$, $ ext{CourtMedianDrift}_{t}$ = Institutional climate drift measures.
  • $ ext{AppointingPresDistanceToFilibusterPivot}_{t}$ = Absolute distance between appointing president’s ideology and filibuster pivot senator’s ideology at time of confirmation.
  • $ ext{AppointingPresApproval}_{t}$ = Appointing president’s approval rating at confirmation.
  • $ ext{YearsAsFederalJudge}_{it}$ = Prior federal judge service years before Supreme Court confirmation.
  • $ui$ = random effect for justice i; $ u{it}$ = error term.
• Note: The study also presents a term-by-term variation analysis (Table 2) where the same regression is estimated cumulatively with Terms Served restricted to the first 1, 1–2, 1–3, …, 1–12 terms to identify the point at which drift becomes statistically detectable.

Key Findings from Table 1 (GLS Random Effects; 1937–2007)

• Main effect of Terms Served by Justice on drift (primary finding):
  • Coefficient for Terms Served by Justice: eta_1 = 0.0099 with standard error SE = 0.002, highly significant (*** p < 0.01).
  • Interpretation: Each additional term served increases the drift score by about 0.01 on the Common Space scale, on average.
• Other control variables (mostly not statistically significant in Table 1):
  • Congressional Drift: eta_2 = 0.1689, SE ≈ 0.138 (not statistically significant).
  • Presidential Drift: eta_3 = 0.0002, SE ≈ 0.017 (not significant).
  • Court Median Drift: eta_4 = -0.1113, SE ≈ 0.082 (not significant).
  • Appointing President’s Distance to Filibuster Pivot: eta_5 = 0.2862, SE ≈ 0.199 (not significant).
  • Appointing President’s Approval Rating: eta_6 = 0.0012, SE ≈ 0.005 (not significant).
  • Years Served as Federal Judge: eta_7 = -0.0017, SE ≈ 0.008 (not significant).
• Model fit and diagnostics (Table 1):
  • Observations: 611 justice-terms; Justices: 35.
  • Rho (random-effects variance component): 0.88 (high intra-justice correlation).
  • Variance inflation factor (mean): 3.63 (no severe multicollinearity).
  • Wald chi-squared statistic: ext{Wald} \chi^2 = 27.33 with *** significance.
• Interpretation offered by authors: The central effect is the accumulative term effect; while institutional climate variables show no robust, consistent impact in Table 1, the term-length effect remains the primary driver of drift away from the appointing president’s ideology.

Key Findings from Table 2 (Term-Interval Analysis)

• Purpose: Identify the tenure point where drift becomes statistically significant by incrementally increasing the number of terms considered (1–9, 1–10, …, 1–12).
• Results (coefficients on Terms Served by Justice with robust SEs):
  • 1–9 terms: eta ext{ on Terms Served} = 0.0091, ext{ SE} = 0.008, ext{ p} = 0.242 (not significant)
  • 1–10 terms: eta = 0.0108, ext{ SE} = 0.006, ext{ p} \approx 0.070 (marginal)
  • 1–11 terms: eta = 0.0129, ext{ SE} = 0.005, ext{ p} \approx 0.017 (significant at p<0.05)
  • 1–12 terms: eta = 0.0139, ext{ SE} = 0.005, ext{ p} \approx 0.006 (significant at p<0.01)
• Beyond 12 terms: The effect remains statistically significant at p < 0.01 for terms beyond 12.
• Interpretation: The drift toward independence from the appointing president’s ideology becomes statistically meaningful after roughly the 11th–12th term; the authors emphasize that ten terms is the threshold where concerns become germane, aligning with Calabresi and Lindgren’s discussions while highlighting the timing of drift rather than just average tenure length.
• Figure 1 (visual): Graphically depicts the rise of average yearly drift across terms served, illustrating a gradual increase in drift as tenure lengthens.

How to Interpret the Findings (Thematic Takeaways)

• Acclimation dynamics: Early on, justices exhibit stronger alignment with appointing presidents due to dependence on nomination, information, and political capital; as tenure increases, they progressively detach and act with greater judicial independence.
• Timing of the drift: The study identifies a clear temporal pattern—drift accelerates as justices accumulate terms, with the statistical breakpoint around terms 11–12. This provides a concrete, testable anchor for term-limit debates.
• Robustness of the main effect: Even after controlling for confirmation conditions and shifts in congressional/presidential/Court ideology, the effect of Terms Served remains significant, underscoring a systemic, tenure-related drift mechanism.
• Null findings for institutional variables: In Table 1, the postconfirmation institutional variables (Congressional Drift, Presidential Drift, Court Median Drift) do not show robust, consistent effects on justice-voting alignment with the appointing president. This suggests that the primary driver of drift in this analysis is the passage of time (tenure), not immediate shifts in the broader political environment captured by those controls.
• Implications for democratic theory and term limits:
  • The observed trend supports arguments that the influence of a president on a justice wanes over time, which is compatible with a gradual move toward independent judgment.
  • However, the accumulation of drift raises concerns for democratic accountability: if justices drift away from the appointing president’s ideology as tenure lengthens, proponents of term limits can point to a measurable mechanism by which accountability could be reinforced.
  • Conversely, advocates for a robust, independent judiciary may stress that increasing independence over time is a feature, not a flaw, of the Court’s legitimacy.

Policy Implications and the Case for Term Limits

• Core policy suggestion: Because drift becomes statistically detectable after around the 11th term, a fixed-term limit could help maintain a link between the public’s democratic will and Court outcomes without fully sacrificing independence.
• Specific proposal discussed: A nonrenewable fixed term of around ten terms (or equivalently, a fixed number of years) that staggers appointments across presidencies could provide a balance—allowing each president to influence the Court while ensuring turnover that keeps the Court responsive to public preferences.
• The authors connect to prior work arguing for term limits (Calabresi & Lindgren 2006; Stras & Scott 2007) and engage with broader debates about life tenure versus fixed terms. They explicitly discuss the idea that fixed terms could preserve independence by decoupling continuation in office from ongoing political approval, following Monaghan’s perspective.
• Ethical and philosophical considerations touched:
  • Independence: Complete independence is valued by the Founders and many scholars as essential to the Court’s legitimacy.
  • Democratic accountability: The public’s preferences should have indirect influence on constitutional interpretation, potentially through appointment turnover.
  • Trade-offs: Term limits may introduce political recalibration and affect strategic appointments, but could also mitigate concerns about “undemocratic” life tenure.

Connections to Foundational Works and Related Literature

• Foundational thought on judicial independence and presidential power: Hamilton, Scigliano, and other Founders’ perspectives on the Court as a distinct and potentially independent branch.
• Related empirical lines: Prior studies on the acclimation effect (e.g., Brenner & Hagle; Hurwitz & Stefko) and new institutionalist work (Clayton & Gillman; Murphy; Epstein et al.) on executive–judicial dynamics.
• Key empirical anchors cited by Sharma & Glennon:
  • Epstein, Knight, and Martin (2001, 2007a, 2007b) on the Judicial Common Space and the interaction of judicial behavior with presidential and legislative actors.
  • Segal, Timpone, and Howard (2000); Epstein & Segal (2005); Epstein, Segal, Martin, & Westerdale (2007) on ideological drift and congruence between presidents and justices.
  • Calabresi & Lindgren (2006) and Stras & Scott (2007) on life tenure, retirement, and tenure length dynamics.
  • Bailey, Kamoie, and Maltzman (2005) on information flows (solicitor general) and initial congruence for new justices.

Limitations and Areas for Future Research

• Scope limitation: The analysis focuses on drift relative to appointing presidents’ ideologies and does not model selection of cases or issue-area specialization directly.
• Alternative appointment dynamics: The paper notes that some appointments may be influenced by informational or demographic considerations beyond ideology; future work could incorporate these factors.
• Additional mechanisms: While institutional variables did not show robust effects here, more granular measures of executive–legislative–court interactions or other political processes could refine understanding of drift drivers.
• Generalizability: The study covers 1937–2007 terms; extending the period and incorporating newer justices would test whether patterns persist.

Summary of Core Takeaways

• The main claim is that justices drift ideologically away from their appointing presidents with each additional term on the Court, with measurable drift beginning in the latter stages of tenure (roughly 11th–12th terms).
• This has direct implications for debates about Supreme Court term limits as a mechanism to preserve democratic accountability without fully sacrificing independence.
• The analysis provides a precise, term-by-term view rather than relying on broad tenure-length categories, strengthening the case for considering fixed-term limits as a policy option.
• The findings support a synthesized view: early- tenure congruence may occur due to acclimation and informational dynamics, while later tenure reflects increasing independence, a core tenet of new-institutionalist perspectives.

Quick Reference: Key Terms and Notation

• Justice Drift Score (JDS):
  • Definition: Absolute distance between a justice’s Judicial Common Space score in a term and the appointing president’s Common Space score in that term.
  • Directional drift adjustment: In some analyses, drift is set to 0 if the drift would move toward the appointing president’s ideology under specified partisan conditions.
• Terms Served by Justice: Continuous measure from 1 to 37 terms.
• Appointing President’s Distance to Filibuster Pivot: Absolute ideological distance between the appointing president and the pivotal senator at confirmation; used to proxy confirmation dynamics under partisan opposition.
• Constitutional and Political Contexts (controls): Congressional Drift, Presidential Drift, Court Median Drift, Appointing President’s Approval, Years Served as Federal Judge, etc.

Notable Data Points (selected from Tables in the Article)

• Sample size and structure: 611 justice-term observations; 35 justices; 1937–2007 terms.
• Descriptive drift: Mean drift score ≈ 0.352; range 0 to 1.17.
• Main effect: Terms Served by Justice → Drift: eta_1 = 0.0099, SE ≈ 0.002, p < 0.01 (Table 1).
• Other controls (Table 1): not statistically significant in the main model (e.g., Congressional Drift, Presidential Drift, Court Median Drift).
• Term-by-term results (Table 2): drift becomes statistically significant at Term 11 (p ≈ 0.017) and stronger at Term 12 (p ≈ 0.006); overall significance remains beyond Term 12 (p < 0.01).
• Model diagnostics (Table 1): Rho ≈ 0.88; robust SEs; Wald χ² ≈ 27.33***; mean VIF ≈ 3.63.
• Threshold interpretation: The authors argue that ten terms is a meaningful benchmark for policy consideration, with drift becoming substantively important after about the eleventh term.

Representative Excerpt (Conceptual Reference)

• “Thus a justice’s voting score will drift further from his or her appointing president’s ideology score over time, even after controlling for the other variables in the model.” (Discussion of Table 1).
• “Table 2 effectively suggests that Calabresi and Lindgren (2006) are addressing a relevant consideration when they discuss Supreme Court term limits—although we choose to focus on a different aspect of that discussion. Specifically,… ten terms served is the point after which these concerns become most germane.”

End Notes

• This set of notes condenses the theoretical framing, data construction, empirical strategy, main results, and policy implications from Sharma & Glennon’s study on appointing presidents, justices, and the case for term limits.
• For deeper detail, consult the article: Sharma, Hemant, and Colin Glennon. 2013. A Case for Supreme Court Term Limits? The Changing Ideological Relationship between Appointing Presidents and Supreme Court Justices. Politics & Policy, 41(2): 267–297.