What are the historical Senate vote totals in presidential impeachment trials and what do they reveal about chances for conviction?

1. Historical vote totals: the hard numbers and who mattered

Only three presidents have been tried by the Senate—Andrew Johnson, Bill Clinton and Donald Trump (twice)—and none were convicted; Andrew Johnson’s critical roll calls produced 35 guilty to 19 not guilty on the articles that were voted, each one vote short of the two‑thirds needed to convict in that era ^{[3] [4]}, Bill Clinton was acquitted by the Senate after House impeachment and thus did not reach the two‑thirds conviction threshold (the Constitution requires two‑thirds of Senators present) ^{[2] [1]}, Donald Trump’s first trial produced votes of 48–52 and 47–53 on the two articles—well short of 67—and his second impeachment produced a 57–43 guilty vote, the largest bipartisan conviction tally in modern history but still ten votes shy of conviction ^{[5] [6] [7]}.

2. Party alignment and exceptions: why raw numbers mask the political reality

Vote totals in presidential trials have tracked partisan divisions strongly: Johnson’s votes reflected fierce intra‑party fractures post‑Civil War but still fell just short ^[3], Clinton’s Senate acquittal was driven by a party‑aligned Senate that refused to reach two‑thirds ^[2], and Trump’s trials show the same pattern—near‑party voting with only a handful of cross‑party defections (Mitt Romney in the first trial and seven Republican senators in the second) that were historically notable but numerically insufficient to meet the constitutional bar ^{[8] [7] [6]}.

3. The two‑thirds rule: constitutional design and practical consequence

The Constitution’s two‑thirds requirement for conviction in the Senate (Article I, Section 3) is explicit and has been the decisive structural constraint on removal; when mapped onto contemporary party polarization, that supermajority rule means a majority in the House can impeach but the Senate will only convict if there is a substantial bipartisan consensus—an outcome rare in modern polarized politics ^{[1] [2]}. Historical and comparative examples beyond presidents—such as the Samuel Chase judicial impeachment where majorities voted guilty on some articles but did not reach two‑thirds—underscore that the Senate has repeatedly resisted converting simple majorities into removals ^[9].

4. What the vote totals reveal about chances for conviction going forward

The empirical lesson is blunt: conviction requires either overwhelming evidence that collapses party loyalty or a Senate composition with a large cross‑partisan bloc willing to join a majority party in removal; absent those conditions, even a sizable bipartisan minority—like the seven Republicans who voted to convict in Trump’s second trial—will not suffice to secure conviction ^{[6] [7]}. The mathematical reality is immutable: in a 100‑member Senate the ceiling for conviction without 17 cross‑party defections is insurmountable, so political dynamics and institutional norms (including procedural choices about witnesses and evidence) usually determine outcomes more than raw factual proofs alone ^{[1] [10]}.

5. Important caveats and institutional factors that shape vote totals

Historical vote totals must be read with caution: procedural rulings, questions about jurisdiction (as with the post‑term trial doctrine debated in Trump’s second trial), variations in Senate rules, and strategic decisions by managers and the White House affect whether particular articles are voted on or whether trials are even completed—William Belknap’s 1876 case, for example, involved a 37–29 Senate decision on jurisdiction though it ended in acquittal, showing procedural edges can shape final tallies ^{[11] [6]}. Additionally, sources differ in emphasis and not all provide every granular roll call for older cases; the reporting here relies on Senate records and contemporary accounts that consistently show the two‑thirds rule as the decisive barrier ^{[3] [4] [2]}.