FILE - In this May 7, 2014 file photo, Illinois Gov. Pat Quinn speaks to members of the Illinois Manufacturer's Association in Springfield Ill. Quinn has banked about $12 million for his November re-election bid. The Chicago Democrat released his second-quarter campaign finance report Tuesday July 15, 2014. It shows Quinn raised about $3.7 million in the three-month period that ended June 30. The race between Quinn and Republican businessman Bruce Rauner (ROW'-nur) is expected to be one of the most competitive â€” and costly â€” in the nation. (AP Photo/Seth Perlman,File)
FILE - In this June 12, 1014 photo Illinois Republican gubernatorial candidate Bruce Rauner speaks at a news conference in Chicago. Rauner says he raised about $8 million in the second quarter and has about $3.5 million on hand for his bid for Illinois governor. The Winnetka businessman's campaign released fundraising totals Tuesday July 15, 2014 for the three-month period that ended June 30. The race between Rauner and Democratic Gov. Pat Quinn is expected to be one of the most competitive â€” and costly â€” in the nation. (AP Photo/M. Spencer Green, File)
CHICAGO — Democratic Gov. Pat Quinn and Republican Bruce Rauner are setting up a big-money battle for Illinois governor, hauling in millions for a highly competitive race one campaign finance expert predicts could see more than double the spending of four years ago.
Quinn raised about $3.7 million in the three-month period that ended June 30, according to second-quarter campaign finance filings, and has about $12 million in his campaign fund. His biggest donors were labor unions and the Democratic Governors Association, though Quinn said in a statement more than two-thirds of his contributors $100 or less.
"I'm grateful to have the support of everyday people across Illinois as we continue to tackle the tough issues and get the job done," said Quinn, who's seeking his second full term.
Rauner raised double the amount of Quinn in the same quarter but spent millions more, leaving him with about $3.5 million. But the multimillionaire — who already has given more than $6 million to his own campaign — has the personal wealth and fundraising network to easily make up the difference with Quinn.
His totals include a $2.5 million donation from Chicago hedge fund CEO Ken Griffin. The money, given last month, is believed to be the largest single Illinois campaign contribution in the post-Watergate era, and brings Griffin's total donations to Rauner's campaign to more than $3.5 million.
The Winnetka businessman's campaign also said via twitter that 80 percent of its more than 8,000 donations were for $100 or less.
The spending is a sign of how competitive the race is and how badly Republicans would like to take control of a blue state that's also home to President Barack Obama. The Republican Governors Association has called Illinois one of its top 2014 targets, and already has sunk $1.5 million into the race.
Democrats and their allies in organized labor are working ferociously to hold on to the seat and prevent Rauner — whose anti-union positions are seen as a huge threat — from winning his first bid for public office.
That means fundraising numbers for the Nov. 4 election "are going to be huge," said Kent Redfield, an emeritus professor of political science at the University of Illinois at Springfield and campaign finance expert.
In 2010, Quinn and his GOP rival, state Sen. Bill Brady, spent about $32 million combined, Redfield said.
"Double that is a conservative estimate" for the 2014 race, Redfield predicted.
Rauner, who defeated three candidates to win the GOP primary, has already been spending heavily on TV advertising and other areas. Quinn has benefited from not having a costly Democratic primary and from the name recognition that comes from incumbency and decades of political activity.
Follow Sara Burnett at https://twitter.com/sara_burnett.