State filings show Illinois' richest man, Ken Griffin, pitching in $250,000 to Rauner's campaign.
It's the second time this week Rauner received a donation worth a quarter of a million dollars.
Previously, those donors could have only give two-percent as much.
After the downfall of Gov. Rod Blagojevich, Illinois put a limit on campaign contributions. This would have been the first governor's race they were put into effect.
Instead, Rauner, himself a wealthy businessman, lifted the caps for the primary race when he gave his campaign $500,000 of his own money earlier this month.
Both of Rauner's biggest contributors have previous ties to Democrats.
Former CEO of AllScripts Glenn Tullman donated to Gov. Pat Quinn in the last governor's race. And Griffin, who's President of Citadel, helped out Chicago Democratic Mayor Rahm Emanuel to the tune of $100,000.
This isn't the first time Griffin has helped a candidate promising to change how things are done in Springfield.
Back in 2002 and 2003, Griffin gave $70,000 to Rod Blagojevich.