The race for Illinois governor will be a battle between two deep-pocketed candidates who’ve already sunk more than $120 million of their own money into the contest, putting it on pace to become the costliest such campaign in U.S. history.

Republican Gov. Bruce Rauner, a wealthy former private equity investor, defeated conservative state Rep. Jeanne Ives on Tuesday for the GOP nomination.

“We are in a critical time, a critical turning point in Illinois,” Rauner told supporters. “I am humbled by this victory. You have given me a chance to win the battle against corruption that plagues Illinois.”

He will face Democratic billionaire J.B. Pritzker, an investor and heir to the Hyatt hotel fortune. Pritzker easily won the primary over Chris Kennedy, the son of the late Sen. Robert F. Kennedy; and Daniel Biss, 40, a state senator who campaigned as the “middle-class candidate.”

Pritzker, 53, already has spent more than $70 million to bankroll his campaign, while Rauner has put in about $50 million and has received millions more from his wealthy friends in the business community. Combined they’re expected to top California in 2010 as the nation’s most expensive governor’s race.

Pritzker pledged to defeat Rauner but told supporters “we have a real fight ahead of us.”