WASHINGTON - With Republican super PACs a growing force in the 2012 presidential election, Minnesota's Al Franken is joining other Senate Democrats in spearheading legislation to raise disclosure standards on independent groups that run political ads around campaigns.

The effort was announced Wednesday after a slew of new campaign reports highlighted the major role of so-called super political action committees in the GOP presidential primaries. Those primaries have been dominated in recent weeks by negative ads in Iowa, New Hampshire, South Carolina and Florida.

The first significant round of campaign reports divulging super PAC donors came Tuesday, after voters had made their choices in the first decisive primary and caucus states. Critics have called for more timely disclosure.

Democrats also have targeted nonprofit advocacy groups that run issue ads in elections but generally don't have to disclose their donors. Together, super PACs and other outside groups have spent an estimated $15 million in the 2012 elections. That's 43 percent of total campaign spending so far.

Franken and his allies have yet to draft a bill but have long lamented the lower level of disclosure and accountability allowed under rules established in the 2010 Citizens United decision, a Supreme Court case that toppled limits on political spending by corporations, wealthy individuals and unions.

"It's just going to get worse," Franken said. "We have to make some changes or the American people are going to get so cynical, as we know they already are."

Franken and fellow Democrats have had little success in the past trying to stem the flow of wealthy donor money or imposing greater disclosure requirements.

"This is just turning people off," Franken said of the rising trend of hidden money financing increasingly harsh campaign messages.

'We find it hypocritical'

A spokesman for Senate Republican Leader Mitch McConnell had no comment. But other Republicans say they're playing by the same rules that allow big unions and liberal nonprofits to back Democratic candidates.

"They can argue that this is the death of democracy, but they're perfectly happy to play in that space, as well," said Brian Walsh, who runs the Congressional Leadership Fund, a super PAC chaired by Minnesota Republican Norm Coleman, who lost his Senate seat to Franken in 2009.

"We find it hypocritical that they didn't have much of a problem with some of the unions spending upwards of $60-$70-or-$80 million on the political process, but once you have folks on the center-right or the conservative side of the aisle who now have the opportunity following the Citizens United case to do the same, that suddenly it's an injustice of democracy."

Walsh said the Congressional Leadership Fund, which has raised $130,000 since its inception last fall, will continue raising money to help Republicans keep their House majority. One seat they will probably protect is that of freshman Republican Chip Cravaack in northern Minnesota.

"We're watching that very closely," said Walsh, whose super PAC board includes former GOP Rep. Vin Weber of Minnesota.

A super PAC backing Republican presidential candidate Mitt Romney filed reports this week showing it raised $30 million last year, while American Crossroads, a super PAC connected to GOP strategist Karl Rove, raised $18 million. Together, they outstripped the leading Democratic super PACs, a trend that could offset President Obama's fundraising advantage over Romney, the GOP front-runner.

Chances of overhaul slim

Democrats note that the money raised by the American Crossroads super PAC, whose donors must be reported, was dwarfed by the $33 million raised by its nonprofit affiliate, Crossroads GPS, which does not have to disclose donors.

"We're now living in the world created by Citizens United," said Sen. Charles Schumer, third-ranking Democrat in the Senate.

Citizens United covered unions, as well, but Schumer said organizations funded by union dues cannot match the fundraising prowess of corporate America. "No matter who does it, the system needs to be fundamentally changed," he said.

Both sides agree that the prospects for reform legislation passing before the November elections are slim. Republicans beat back a similar effort in 2010.

Nevertheless, Democrats promised a series of Senate hearings to keep the issue in the public eye as the election year rolls on.

Kevin Diaz is a correspondent in the Star Tribune Washington Bureau.