The 2018 Illinois governor's race is on pace to be the most expensive in U.S. history, propelled by a wealthy Republican incumbent and a billionaire Democrat. J.B. Pritzker, one of the world's richest people, is among several Democrats trying to defeat multimillionaire Rauner.
Both Pritzker and Rauner have been airing TV ads more than a year before Election Day. Combined, all of the candidates have raised more than $100 million in the past year.
The Associated Press contributed to this report.