What are historical examples of presidential impeachments and which factors determined whether the Senate convicted?
Executive summary
Three Presidents—Andrew Johnson, Bill Clinton and Donald Trump—have been impeached by the House; none were convicted by the Senate, while Richard Nixon resigned before the House completed impeachment [1] [2] [3] [4]. Across all federal impeachments, only eight officials—each a federal judge—have been convicted and removed by the Senate, illustrating that conviction is rare and shaped as much by politics and timing as by legal argument [5] [6].
1. A short catalogue of presidential impeachments and their Senate outcomes
Andrew Johnson was impeached in 1868 for removing Secretary of War Edwin Stanton and for attacks on Congress; the Senate voted 35 guilty to 19 not guilty on the leading article—one vote short of the two‑thirds needed for conviction—then failed by the same margin on two other articles [7] [8]. Bill Clinton was impeached in 1998 on charges of perjury and obstruction; the Senate acquitted him, with 45 senators voting to convict on the perjury count and 50 on obstruction, both well short of the 67 votes required [2]. Donald Trump was impeached twice; in his first trial the Senate acquitted him on both articles with a largely party‑line vote and only one senator crossing to convict on one article (Mitt Romney) [9], and in his second trial the Senate fell short again—57 guilty to 43 not guilty on “incitement” despite bipartisan defections, below the supermajority threshold [9] [3]. Richard Nixon resigned before a full House vote made conviction likely [4].
2. The constitutional and procedural hurdle: two‑thirds and trial rules
The Constitution assigns the House the power to impeach and the Senate to try impeachments, and it requires the “concurrence of two‑thirds of the Members present” to convict and remove an officer—an intentionally high bar that makes convictions exceptional [10] [2]. Senate trial procedures add practical constraints: the Chief Justice presides at presidential trials, managers from the House prosecute, and the Senate decides evidentiary and threshold issues that can shape the outcome [10] [6].
3. Legal arguments versus political judgment: what senators weigh
Senators have disagreed about whether impeachment requires a criminal statute to be violated or whether “high crimes and misdemeanors” can include political misconduct, with some voting patterns reflecting legal judgment and others reflecting political calculation [3] [11]. The Johnson trial turned on statutory interpretation of the Tenure of Office Act and the constitutionality of Johnson’s actions [8], while Clinton’s managers framed perjury and obstruction as corruption of the justice system and defenders argued the evidence did not meet the constitutional standard for removal [4].
4. Timing, partisanship and public opinion as decisive variables
Temporal context matters: the Constitution Center notes that proximity to elections and fears of political backlash influenced senators in 1868, and modern trials have been deeply partisan affairs where party loyalty and public opinion play outsized roles [1] [12]. Senate party control often sets the baseline: a Senate aligned with the president’s party makes a supermajority conviction structurally unlikely, and public approval can make senators reluctant to oust a president absent overwhelming consensus [2] [12].
5. Institutional precedent, norms and downstream incentives
Historical practice—how past impeachments and convictions were treated—shapes what senators view as legitimate grounds for removal, and institutional incentives (preserving Senate prerogatives, avoiding a precedent of removing political adversaries) frequently counsel restraint [11] [1]. The rarity of convictions (only eight removals overall, all judges) underscores a Senate tendency to reserve removal for clear abuses crossing into criminality or blatant betrayal of office, though that standard has been interpreted variably over time [5] [11].
6. Conclusion: conviction is legal threshold plus political calculus
The historical record shows convictions are the product of both constitutional mechanics—a supermajority requirement and trial rules—and political realities: party composition, public sentiment, timing, legal framing, and institutional norms [10] [1] [2]. Reporting and scholarship converge on this dual explanation: impeachment can be legally justified on paper, but conviction in the Senate requires a political coalition willing to remove a president, which history demonstrates is difficult to assemble [6] [12].