After previously stating that he would not run for re-election, Jason Chaffetz announced on May 19 that he was resigning his seat in the House, effective June 30. A special election was called to replace him with a filing period opening on May 19 and closing by June 30, an expected primary date of August 15, and an election day of November 7.
A crowded field of candidates emerged to compete for spots in their respective parties' primaries. 15 Republicans, 4 Democrats, 2 Independent American Party members and 1 Libertarian declared their candidacy. Candidates could qualify for the primary ballot by either being nominated by delegates at their party's convention or gathering 7,000 signatures from registered voters. Those gathering signatures could also seek nomination at their party's convention. The Republican and Democratic parties held conventions June 17 to select a nominee from the declared.
The primary election to determine the Republican Party's candidate for the general election was held on August 15. In addition to the partisan candidates, one unaffiliated candidate appeared on the general election ballot and two candidates ran as a write-in.
The general election was held on Tuesday, November 7, 2017. Republican John Curtis was declared the winner and was subsequently seated by the U.S. House for a term that ends January 3, 2019.
The Republican primary was held on Tuesday August 15, 2017. Only registered Republicans living in the 3rd congressional district were able vote in the primary, though unaffiliated voters were allowed to affiliate as Republicans at polling locations on election day.
Fifteen candidates declared their candidacy for the Republican party nomination. While four candidates declared their intent to gather signatures, only two submitted signatures for verification by the required deadline. This election was the first time in Utah politics where three candidates were on the primary ballot since two candidates submitted enough signatures to qualify for the primary ballot and the party nominated a third candidate at its convention.
Ainge and Curtis submitted enough signatures to qualify for spots on the primary ballot. Curtis also participated in the convention process, but lost to Herrod who was nominated at the convention. Curtis would go on to win the primary.