Incumbent Jim Risch holds a commanding lead in Idaho's Republican Senate primary, scheduled for May 19, 2026, as traders price his extensive Senate tenure since 2009 and broad party support against three lesser-known challengers including Joe Evans. Risch's fundraising edge, established voter base in the solidly Republican state, and Trump endorsement have kept challengers fragmented with minimal momentum in recent filings and voter guides. The market's near-certainty reflects these structural advantages in a low-turnout primary environment. A realistic shift would require an unforeseen late surge in challenger visibility or turnout patterns that overcome the incumbent's organizational and name-recognition strengths before ballots close.