Supermajority
A supermajority is a voting requirement exceeding a simple majority—typically two-thirds or three-fifths of members present and voting—mandating broader consensus for passage of proposals in legislative bodies, constitutions, and organizations.[1][2]
Such thresholds are employed to safeguard against transient majorities enacting profound or irreversible changes, as seen in constitutional amendment processes where most U.S. states demand legislative supermajorities alongside ratification.[3][4]
In the U.S. federal system, the Constitution specifies two-thirds votes in both houses of Congress for overriding presidential vetoes, proposing amendments, and approving treaties in the Senate, while state legislatures often apply similar rules to tax increases or budget overrides.[4][5][6]
Supermajorities promote institutional stability by requiring cross-partisan support but have drawn critique for enabling obstruction, particularly in polarized environments where achieving them proves challenging without compromising on core policy differences.[7][8]
Conceptual Foundations
Definition and Core Principles
A supermajority refers to a voting requirement exceeding a simple majority, typically mandating two-thirds or three-fifths support among members present and voting for a measure to pass.[4][9] This threshold ensures decisions reflect broader consensus beyond narrow pluralities, distinguishing it from ordinary legislation that often proceeds by simple majority (over 50 percent plus one).[8] In legislative contexts, such as the U.S. Congress, the Constitution specifies supermajorities for actions like overriding presidential vetoes or ratifying treaties, calculated as two-thirds of members voting with a quorum present.[4] The core principle underlying supermajorities derives from the need to mitigate risks of transient majorities enacting policies that could destabilize institutions or infringe on minority interests.[7] By elevating the approval bar, these rules compel deliberation and compromise, fostering outcomes more likely to endure scrutiny and reflect sustained public preference over ephemeral shifts.[10] This mechanism counters the potential for simple majorities to pursue short-term gains at the expense of long-term stability, as evidenced in constitutional designs where irreversible changes, like amendments, demand supermajority assent to approximate unanimity in pivotal matters.[7] Supermajorities also embody a commitment to protecting entrenched norms against hasty alteration, recognizing that certain decisions—such as altering fundamental laws or corporate charters—warrant safeguards against factional dominance.[11] In practice, this principle manifests in varied thresholds tailored to decision gravity; for instance, lower-stakes votes may suffice with simple majorities, while high-impact ones invoke supermajorities to ensure robust backing and reduce reversal likelihood.[12] Empirical application in bodies like the U.S. Senate underscores this, where 60-vote thresholds for cloture effectively approximate supermajority hurdles to advance debate.[13]First-Principles Rationale
Supermajority requirements emerge from the foundational principle that decision-making thresholds in collective governance should scale with the stakes and irreversibility of outcomes, distinguishing routine policy from structural alterations that bind future actors or generations. In low-stakes, reversible decisions, a simple majority efficiently aggregates preferences while minimizing deadlock, but for high-stakes changes—such as constitutional amendments or overrides of executive vetoes—a bare majority risks entrenching transient passions or factional impulses that do not reflect enduring consensus.[10] This calibration reduces the probability of erroneous commitments by demanding a stronger signal of support, akin to evidentiary standards in adjudication where greater certainty is warranted for severe consequences.[14] Causally, simple majorities can perpetuate instability through preference cycling or short-term biases, where voters prioritize immediate gains over long-term viability, leading to policy oscillations that erode trust and efficacy. Supermajorities counteract this by imposing transaction costs that filter marginal proposals, compelling proponents to build cross-factional coalitions and thereby enhancing legislative quality and legitimacy—opponents of a measure gain incentives to acquiesce when the threshold demands near-universal buy-in.[15] In diverse polities, this mechanism mitigates risks of majority overreach by protecting entrenched minorities without vesting veto power in them, fostering deliberation over dominance and aligning outcomes more closely with underlying social equilibria rather than episodic majorities.[10] Empirically grounded reasoning further underscores that supermajorities preserve institutional continuity against myopic reforms; for instance, entrenchment rules address voters' tendency to evaluate legislators on proximate effects, deterring hasty dilutions of foundational pacts that safeguard against arbitrary power shifts.[14] While critics contend such thresholds may entrench status quo biases, the first-principles case prioritizes error minimization in irreversible domains, where the cost of false positives (unwise changes) exceeds that of false negatives (delayed reforms), ensuring governance reflects robust rather than fragile agreement.[16]Historical Development
Ancient and Pre-Modern Origins
Supermajority requirements first emerged in the Roman Republic during jury trials in the quaestiones perpetuae, specialized courts established from the late second century BCE onward, where convictions of elites such as senators often demanded a vote exceeding simple majority—typically 25 of 51 jurors—to mitigate risks of politically motivated condemnations.[17][18] This mechanism reflected an early institutional preference for heightened consensus in high-stakes judicial decisions, prioritizing protection against erroneous or factional outcomes over expediency.[19] In ancient Greece, decision-making in assemblies like those described in Homeric epics relied primarily on acclamation—collective shouting or gestures—rather than counted votes, with the shift to numerical aggregation occurring in archaic poleis around the sixth century BCE, though formalized supermajorities remained rare and typically manifested as quorums rather than proportional thresholds.[20] For instance, Athenian ostracism procedures required at least 6,000 votes to exile a citizen, functioning as an absolute quorum to ensure broad participation but not a relative supermajority beyond half.[21] Pre-modern developments intensified in medieval ecclesiastical governance, where twelfth-century canon law transitioned from unanimitas (unanimity), rooted in the ideal of moral infallibility and the sanior pars (sounder part) doctrine emphasizing qualitative consensus among the wise, to quantitative supermajority rules for practicality amid growing schisms.[18] The Third Lateran Council of 1179 formalized this shift by mandating a two-thirds majority of cardinals for valid papal elections, restricting voting to cardinals alone and aiming to prevent invalidations from minority dissent while avoiding prolonged vacancies.[22][23] This rule, enduring with modifications until 1996, exemplified supermajority's role in stabilizing hierarchical institutions by demanding broader agreement than simple majorities.[19] Similar thresholds appeared in monastic chapters and early universities for electing superiors, reflecting a broader canonistic trend toward calibrated majorities to reconcile deliberation with decisiveness.[24]Modern Constitutional Adoption
The United States Constitution of 1787 incorporated supermajority thresholds as a core mechanism for high-stakes decisions, reflecting framers' intent to balance majoritarian democracy with safeguards against transient majorities. Article V mandates a two-thirds vote in both houses of Congress to propose constitutional amendments, followed by ratification by three-fourths of state legislatures or conventions, a design adopted on September 17, 1787, to ensure broad consensus for altering the foundational charter. Similarly, Article I, Section 7 requires a two-thirds majority in each chamber to override a presidential veto, a provision ratified to prevent legislative overreach while allowing circumvention of executive checks under exceptional agreement. These thresholds were influenced by colonial experiences with simple majorities leading to instability, prioritizing deliberation over speed in pivotal actions like treaty ratification under Article II, Section 2, which also demands two-thirds Senate approval.[4] In Europe, post-World War II constitutions frequently embedded supermajority requirements to entrench democratic norms against authoritarian reversion, marking a shift toward rigid amendment processes. The Italian Constitution of 1948, promulgated on December 22 after constituent assembly debates, stipulates in Article 138 that amendments require approval by an absolute majority in both chambers followed by a second identical vote or a referendum, effectively imposing a supermajority hurdle through iterative consent to foster stability amid recent fascist history. Germany's Basic Law of 1949, effective May 23, similarly demands a two-thirds majority in the Bundestag and Bundesrat for amendments under Article 79, a threshold adopted during Allied oversight to protect core rights like human dignity from erosion, as evidenced by explicit unamendability clauses paired with high procedural bars. These provisions contrasted with interwar Weimar Germany's simpler majoritarian amendment rules, which had enabled rapid constitutional decay.[25] France's Fifth Republic Constitution, adopted via referendum on October 4, 1958, introduced a three-fifths supermajority in a joint parliamentary session for amendments under Article 89, replacing the Fourth Republic's more flexible procedures that contributed to governmental paralysis. This threshold, proposed by Charles de Gaulle's drafters, aimed to consolidate executive authority while insulating structural changes from factional volatility, requiring either congressional supermajority approval or popular referendum for ratification. Post-colonial and transitional constitutions, such as India's 1950 charter requiring a two-thirds parliamentary majority for amendments under Article 368, further exemplified this trend, with over 100 amendments enacted by 2023 yet constrained by the elevated bar to prevent wholesale rewrites. Empirical patterns show that by the late 20th century, approximately 70% of global constitutions mandated legislative supermajorities for amendments, up from pre-war norms, correlating with efforts to enhance institutional resilience amid ideological conflicts.[26][27][28]Common Thresholds and Variations
Two-Thirds Supermajority
A two-thirds supermajority mandates that a measure receive affirmative votes from at least two-thirds of legislators present and voting, assuming a quorum, to pass.[4] This threshold exceeds a simple majority and serves to ensure broader consensus for significant actions, such as altering fundamental laws or overriding executive decisions. In the United States Constitution, a two-thirds vote is explicitly required in several contexts, including proposing constitutional amendments by Congress under Article V, which necessitates two-thirds approval in both the House of Representatives and the Senate before referral to states for ratification.[30] Similarly, overriding a presidential veto demands two-thirds support in each chamber, as stipulated in Article I, Section 7.[31] The Senate further employs this threshold for ratifying treaties (Article II, Section 2) and convicting officials in impeachment trials (Article I, Section 3), where conviction requires two-thirds of senators present.[5] Expulsion of a member from either chamber also requires a two-thirds vote (Article I, Section 5).[4] Internationally, two-thirds supermajorities appear frequently in presidential systems for veto overrides, particularly in Latin America; for instance, Argentina, Chile, Costa Rica, and El Salvador mandate this level of legislative support to enact bills over executive objection.[32] Many national constitutions adopt two-thirds for amending foundational texts, mirroring the U.S. model by demanding supermajority congressional approval followed by additional ratification steps.[33] In parliamentary contexts, such as the UK House of Commons, internal rules occasionally invoke supermajorities for procedural matters like waiving the three-day rule on bills, though constitutional changes often rely on simple majorities or referendums rather than fixed two-thirds thresholds.[34]| Jurisdiction/Application | Requirement Details |
|---|---|
| U.S. Constitutional Amendments | Two-thirds of both Houses to propose.[30] |
| U.S. Veto Override | Two-thirds in each chamber.[31] |
| U.S. Senate Treaty Ratification | Two-thirds of Senators present.[5] |
| Latin American Veto Overrides (e.g., Argentina, Chile) | Two-thirds legislative majority.[32] |