Earlier this year, Split Ticket released their 2024 Wins Above Replacement (WAR) Model for the 2024 US Election. This model measures how well a candidate outperformed "controlling for seat partisanship, incumbency, demographics, and money", and is intended to be a barometer for candidate quality in Congressional races in both the House and the Senate. For this market, I will only consider incumbent candidates in 2026 (whether or not they win their race).

2024's worst performing incumbents were Senator Deb Fischer (R-NE) at D+17.7 and Representative Ilhan Omar (D:MN-05) at R+13.1. This question will be resolved to the single worst performing incumbent in all of Congress.

https://split-ticket.org/full-wins-above-replacement-war-database/