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.

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.

Experts say 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.