Susan Walsh, Associated Press
Senate Minority Leader Mitch McConnell of Ky. walks to a luncheon on Capitol Hill in Washington, Thursday, June 27, 2013.

LOUISVILLE, Ky. — Senate Minority Leader Mitch McConnell has inserted himself into the latest campaign-finance case before the U.S. Supreme Court, prompting groups opposed to special-interest money in campaigns to take to the airwaves to criticize the Kentucky Republican.

Two nonprofit groups, Public Campaign Action Fund and USAction, on Friday launched a television ad across much of Kentucky that bashes McConnell's role in efforts to persuade the court to strike down limits on campaign contributions.

The 30-second commercial warns a ruling against the contributions cap would set off an unlimited influx of campaign cash from lobbyists, bankers and oil executives.

The ad is airing in the Lexington, Paducah and Bowling Green markets, and the groups called it a six-figure ad buy. The commercial starts by showing a Godzilla-like monster stomping buildings while the narrator says "bigger sure isn't better when it comes to political influence."

McConnell's spokesman didn't immediately respond to an email and phone call on Friday seeking comment.

McConnell isn't a party in the case. But he filed a brief, and his lawyer is scheduled to present the senator's views during oral arguments before the court next week. The court will hear challenges to the limits on aggregate campaign contributions, which restrict an individual donor from giving more than $123,200 in total during the 2014 election cycle.

The ad is scheduled to run in the days leading up to the oral arguments Tuesday and will continue several days after.

"We want Mitch McConnell to explain to Kentuckians why he thinks unlimited political contributions from bailed out bankers and Big Oil CEOs makes our democracy better and America stronger," said David Donnelly, executive director of Public Campaign Action Fund, based in Washington, D.C.

"If the court adopts Sen. McConnell's reasoning, we will have government of, by and for the special interests, not the people."

McConnell has been a leading critic of campaign finance regulations.

He filed a lawsuit challenging the McCain-Feingold campaign finance law and praised a 2010 Supreme Court ruling that freed big business and unions to spend millions directly to sway elections for president and Congress. He said at the time that the ruling restored the First Amendment rights of corporations and unions.

Comment on this story

Kentucky's only Democratic congressman weighed in on the issue Friday. In an op-ed piece appearing in The Courier-Journal, Rep. John Yarmuth said the demise of the campaign contribution limits would further consolidate political power among wealthy donors. And he warned it would open the floodgates to more TV attack ads.

"So this time next year, when you want to throw your DVR through your TV to make the constant noise of attack ads stop, remember who put them there," Yarmuth wrote.

McConnell is facing a tough re-election next year in his bid for a sixth term. McConnell is being challenged in the Republican primary by Louisville businessman Matt Bevin. The Democratic front-runner in the race is Alison Lundergan Grimes, Kentucky's secretary of state.