File photo: Gov. Pat Quinn signed the Religious Freedom and Marriage Fairness Act, making Illinois the 16th state in the nation to legalize same-sex marriage. (CNN)

CHICAGO (AP) — A swanky brunch paying tribute Sunday to those who helped pass Illinois' new same-sex marriage law wasn't free from election-year politics as organizers deemed Gov. Pat Quinn "the most pro-gay governor in the history of Illinois" and knocked his Republican re-election challenger.

Greg Kabel

Quinn faces a difficult bid against businessman Bruce Rauner, who hasn't specified his views on gay marriage but said he'd be open to changing the law if efforts are voter-driven.

Gay marriage hasn't been a major issue in the governor's race where talk of Illinois' massive financial problems has dominated, but it generated headlines this month as the law took effect. Last week Quinn stood at the altar during one longtime couple's wedding and Rauner took heat from activists for not articulating his views.

Art Johnston, founder of Equality Illinois, which pushed for the law, echoed that idea during Sunday's champagne brunch at a downtown hotel attended by both Democrats and Republicans. He praised Quinn's decision to sign the law as a moral one and blasted Rauner without mentioning him by name.

"If he were governor, this June would not be a time of celebration and pride," Johnston said of Rauner before introducing Quinn as "the most pro-gay governor in the history of Illinois."

Other attendees included Chicago Mayor Rahm Emanuel, Republican Comptroller Judy Baar Topinka and state Rep. Tom Cross, one of three House Republicans who voted for the measure last year.

Approving same-sex marriage faced a rough road in Illinois, where some of the state's top religious leaders opposed the idea. While the law took effect statewide June 1, some couples were able to wed earlier because of court rulings.

Rauner's campaign didn't return a message seeking comment Sunday. The venture capitalist from Winnetka has said he doesn't have a social issues agenda in his first bid for public office.

Both Emanuel and Quinn immediately left the event Sunday without addressing reporters as a decision loomed on another major financial issue.

Quinn has a Monday deadline to sign legislation overhauling two Chicago pension systems that hinge on a property tax increase. Emanuel has lobbied for the measure and took time in his Sunday speech about same-sex marriage to praise Quinn as a governor who "shows leadership when there is time for courage."

Quinn has only said the legislation is under review, though he doesn't believe in raising property taxes.