What majority is required in the U.S. House and Senate to override a presidential veto?

1. What the Constitution actually requires

Article I’s Presentment Clause and authoritative treatments say: when the President returns a bill with objections, the originating chamber “reconsider[s]” it and may repass it only if two‑thirds of that chamber agree, and then the other chamber must also approve by two‑thirds for the bill to become law despite the veto ^{[2] [3]}. The Constitution thus sets a two‑thirds supermajority threshold in each chamber as the statutory pathway to override ^[2].

2. Two‑thirds of who? — the practical vote test

Scholarly and institutional sources clarify the two‑thirds requirement applies to “members voting” (i.e., two‑thirds of those present and voting), not necessarily two‑thirds of all elected members — but a quorum must be present for the vote to count ^{[3] [2]}. The Library of Congress notes the Supreme Court has read the clause against the backdrop of quorums and practical chamber procedures ^[2].

3. How the House and Senate proceed — sequential and procedural realities

Congressional practice is sequential: the chamber of origin acts first on a vetoed measure, and only if that chamber achieves the two‑thirds override does the other chamber consider the question ^[3]. House and Senate rules control how quickly reconsideration and the recorded “yea‑and‑nay” votes occur; the CRS and House history pages note overrides are treated as privileged business and typically voted on soon after the veto message arrives ^{[3] [4]}.

4. Why a bill that once had two‑thirds might still fail on override

Voting after a veto is a fresh political moment: members can — and sometimes do — change their votes when asked to override a President’s objections. Commentators and case examples show that even bills that originally passed by large margins have failed override votes because political dynamics shift between passage and reconsideration ^{[5] [6]}. Institutional sources emphasize the rule that the two‑thirds test counts those “voting,” which permits such shifts ^[3].

5. Variations at state level and common misunderstandings

Many state constitutions follow a two‑thirds pattern for gubernatorial veto overrides, but thresholds vary: Ballotpedia documents that while 36 states require two‑thirds, others use three‑fifths or different tests, and some apply the fraction to all elected members rather than those present and voting ^[7]. Confusion often arises when people conflate state rules with the federal rule or assume two‑thirds always means two‑thirds of the chamber’s full membership ^[7].

6. Historical frequency and political significance

Congressional records and historical compilations show overrides are relatively rare in practice: institutional data compiled by Congress and historians indicate a modest percentage of presidential vetoes are overridden ^{[8] [4]}. The CRS notes Congress has overridden vetoes only on a minority of occasions, underscoring that the two‑thirds standard is intentionally high and politically consequential ^[8].

7. Limits and caveats in available reporting

Available sources consistently describe the two‑thirds rule and that it applies to members voting, with procedural caveats ^{[2] [3]}. Sources do not provide a definitive list of every procedural nuance (for example, exact quorum‑counting permutations in every possible House or Senate scenario) so finer technical questions about particular votes or atypical procedural maneuvers are not addressed in the materials provided (not found in current reporting).

Sources cited: National Archives background on vetoes ^[1]; Library of Congress/Constitution Annotated ^[2]; Congressional Research Service and Congress.gov explanations of veto‑override procedure ^{[3] [8]}; House history overview ^[4]; Ballotpedia on state variations ^[7]; explanatory commentary and examples about vote changes after passage ^{[5] [6]}.