The Idaho Senate winner prediction market for 2028 concerns which political party will hold one of Idaho's two U.S. Senate seats after the 2028 election. Idaho is a deeply Republican state, having voted for the Republican presidential candidate in every election since 1968. The state's two current senators, Mike Crapo and Jim Risch, are both Republicans. Crapo was first elected in 1998 and last reelected in 2022. Risch was first elected in 2008 and last reelected in 2020. Risch's term ends in January 2027, while Crapo's term ends in January 2029. The 2028 election will determine who holds the seat currently occupied by Crapo. Crapo has not announced whether he will seek reelection in 2028. He will be 77 years old in 2028. Idaho has not elected a Democrat to the U.S. Senate since Frank Church left office in 1981. The last Democrat to win a Senate election in Idaho was Church in 1974. Since then, Republicans have held both Senate seats continuously. The state's population has grown rapidly, increasing by about 17% between 2010 and 2020. This growth has been driven largely by migration from other states, including some from more politically competitive areas like California and Washington. However, the state's political character remains strongly conservative. The Cook Partisan Voting Index for Idaho is R+18, meaning the state votes 18 percentage points more Republican than the national average. This makes Idaho one of the most Republican states in the country. Any Democratic candidate would face very long odds. The primary election within the Republican Party will likely be the more competitive contest. Several Republicans are potential candidates if Crapo retires. These include Governor Brad Little, Lieutenant Governor Scott Bedke, and Representatives Russ Fulcher and Mike Simpson. The 2028 election will also be influenced by the national political environment. Presidential elections typically drive higher turnout and more party-line voting. The 2028 presidential race will be on the same ballot. This could affect down-ballot races in Idaho, though the state's partisan lean is so strong that national trends may have limited impact. The prediction market resolves based on which party's candidate is sworn in as Senator for the term beginning in January 2029.

Historical Context

Idaho's political history in the 20th century shows a state that was more competitive than it is today. From 1890 to 1950, Idaho elected a mix of Democrats and Republicans to the Senate. Democrat Frank Church served from 1957 to 1981 and was a prominent national figure. Republican James McClure served from 1973 to 1991. The shift to a solidly Republican state began in the 1960s and accelerated in the 1990s. Since 1992, no Democrat has won a statewide election in Idaho. The last Democrat to win a Senate race was Frank Church in 1974. The last Democrat to win a gubernatorial election was Cecil Andrus in 1990. The state's population has grown significantly. In 1990, Idaho had about 1 million residents. By 2020, the population was 1.8 million. This growth has come mostly from domestic migration. People moving to Idaho from other states have tended to be conservative, reinforcing the state's Republican lean. The 2022 Senate election in Idaho saw Crapo defeat his Democratic opponent David Roth by 60.6% to 33.5%. The Libertarian candidate received 5.8%. This result was consistent with recent elections. In 2020, Trump won Idaho with 63.9% of the vote. In 2016, he won with 59.3%. The state's Republican primary is often the decisive election for Senate seats. In 2022, Crapo faced no primary challenger. In 2020, Risch won his primary with 73.5% of the vote against a challenger. The 2028 election will be the first Idaho Senate race since 2022. It will take place during a presidential election year, which typically increases voter turnout. The last time Idaho had an open Senate seat was in 2008, when Larry Craig retired. Jim Risch won that race with 57.7% of the vote. The Democratic candidate, Larry LaRocco, received 34.5%.