2015 Illinois's 18th congressional district special election

The special election for Illinois's 18th congressional district was held on September 10, 2015, between Republican Darin LaHood and Democrat Rob Mellon to fill the remainder of the term of Republican Aaron Schock, who resigned on March 31, 2015. LaHood won the election with almost 68.8% of the vote.

Schock announced on March 17, 2015, that he would resign on March 31, 2015, following allegations of improper spending of political campaign funds and an impending ethics investigation.

According to Illinois state law, Governor Bruce Rauner had to call the special election within five days after Schock's resignation becoming official, and it must be held within 115 days of the call. This would mean that the latest possible day for the election under Illinois law would have been July 29, 2015. However, in order to comply with the federal Uniformed and Overseas Citizens Absentee Voting Act (UOCAVA), the general election was set for September 10, 2015, with party primaries to be held on July 7.

In April 2015, the Marshall County and McLean County governments requested that Schock or his campaign fund reimburse the counties for the special election costs, and two other counties considered similar action. Stark County declined to request reimbursement, as it still had $12,000 left over from the April consolidated election and Schock had not been convicted of a crime.

• Mike Flynn, political strategist and journalist at Breitbart News

• Darin LaHood, State Senator and son of former U.S. Representative Ray LaHood

• Donald Rients, former corrections officer

• Mark Zalcman, attorney. Zalcman stated that he was forced to withdraw because a limited time to file petitions was "done purposely by the Governor to insure that Darin LaHood would not have to face any grassroots opposition in the campaign," and that he would focus on the regular March 2016 primary. Zalcman did not file for the seat in 2016.

• Jason Barickman, state senator

• Bill Brady, state senator, nominee for governor in 2010, and candidate for governor in 2006 and 2014

• Dan Brady, State Representative

• Ed Brady, real estate developer

• Tom Demmer, state representative

• Robert Kent Gray, Jr., attorney and Lincoln Land Community College Trustee

• Bobby Schilling, former U.S. Representative for Illinois's 17th congressional district

• Ryan Spain, Peoria City Councilman

• Jil Tracy, former state representative and candidate for lieutenant governor in 2014

• Michael D. Unes, state representative

• Adam Lopez, member of the Springfield School Board and a Country Financial representative

• Rob Mellon, teacher and candidate in 2014

• Colleen Callahan, State Director for USDA Rural Development and nominee in 2008

• Sonni Choi Williams, deputy corporation counsel for the City of Peoria

• Kristin Dicenso, advisor for the Illinois Department of Transportation

• Jehan Gordon-Booth, State Representative

• Dave Koehler, State Senator

• Andy Manar, State Senator

• John M. Sullivan, State Senator

• List of special elections to the United States House of Representatives

• Mike Flynn for Congress

• Darin Lahood for Congress

• Donald Rients for Congress

• Rob Mellon for Congress