By SARA BURNETT, Associated Press

CHICAGO (AP) — 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 Gov. Bruce Rauner. Both Rauner and Pritzker 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. Most of that comes from Rauner and Pritzker's own money.

Political Data Director Colin Williams says the contest "absolutely" could surpass the most expensive governor's race, a record set in California in 2010. Candidates in that race spent a combined $280 million.