Incumbents lose. Not often — incumbency is one of the most reliable advantages in American politics — but when it happens, it usually signals something larger: a wave year for the opposing party, an unpopular issue position, a redistricting cycle that drew the seat away from its sitting member, or a primary challenge from inside the party.
This page collects every incumbent defeat we have recorded, in either a primary or a general election. Use the historical chart to see which cycles saw the most incumbent turnover (the 2010 cycle, again, stands out). Then browse individual defeats below — filterable by state, chamber, election type, and incumbent party. Click any row to expand the underlying election with full vote totals.
Incumbent Defeats by Cycle
Number of sitting officeholders who lost reelection in each cycle, split between primary defeats (within-party) and general election defeats (across-party).
Browse All Defeats
All Incumbent Defeats
| Year | State | District | Type | Incumbent | Defeated By |
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Methodology
An "incumbent defeat" is recorded any time a candidate marked is_incumbent=true in our database loses a primary, runoff, or general election. We include both legislative and statewide offices. A sitting Democrat losing a Democratic primary counts; a sitting Republican losing a November general counts; an officeholder who runs for a different office and loses does not count (the seat they actually hold is not what's on the ballot).
Primary defeats vs. general defeats. A primary defeat is a within-party loss — the incumbent's own party voters chose someone else. A general defeat is a cross-party loss — voters of the opposite party (or independents) preferred the challenger. The two categories have very different politics behind them: primary defeats are often ideological, general defeats are usually structural (wave years, redistricting, scandal).
Coverage window. 2010 forward. Incumbency flags on candidacies before 2018 are still being backfilled for some states, so historical totals may shift slightly as that data improves. The 2018 cycle onward is fully covered.
What's not included. Incumbents who retire, are term-limited, or run for higher office and then lose that race. Those are tracked on other pages (Open Seats, etc.).