Idaho’s 1st congressional district, encompassing the Panhandle and western Boise area, maintains a strong Republican tilt reflected in its R+22 partisan voting index and consistent double-digit GOP margins in recent presidential and House contests. Incumbent Russ Fulcher secured renomination in the May 2026 primary with 78 percent support and holds a substantial fundraising edge over Democratic nominee Kaylee Peterson. Traders price Fulcher at 95.9 percent implied probability because these structural advantages, combined with the district’s voting history, limit the challenger’s path despite Peterson’s primary victory and campaign focus on issues such as healthcare and immigration. A narrow set of late developments, including major scandals or sharply elevated Democratic turnout, could still shift the outcome before the November 3 general election.