Washington's 4th Congressional District, the state's most conservative seat, is holding a Republican primary on 4 August 2026 that has become a proxy battle over the party's direction after Donald Trump eventually leaves the political stage. The contest, triggered by the retirement of incumbent Dan Newhouse, pits a Trump-endorsed "America First" candidate against a bipartisan-minded state senator and an anti-establishment businessman, making it an unusually clear test of which strain of Republicanism resonates most with voters in a solidly red district.

The three Republican contenders are Yakima County Commissioner Amanda McKinney, who has Trump's and House Speaker Mike Johnson's backing and runs as a staunch MAGA candidate; State Senator Matt Boehnke, who stresses bipartisan cooperation and civility; and businessman Jerrod Sessler, a two-time previous candidate campaigning against career politicians. Air Force veteran John Duresky is expected to win the Democratic side under Washington's top-two primary system, though the district — rural, over 40% Latino and reliant on agriculture and energy — remains reliably Republican even though it once re-elected Newhouse despite his vote to impeach Trump. Notably, a Trump endorsement has yet to guarantee victory in this district's primaries, a track record analysts say makes the outcome a meaningful signal for Republicans planning beyond Trump.