DES MOINES - Karen Dyer, a 70-year-old self-described "farm girl" from Indianola, thought she'd seen a lifetime's worth of political ads going back through her decades of Iowa caucuses.

But the intensity of the past week's air-war blitzkrieg has been jarring, she said, not just for the cacophony of messages, but for their mounting negativity.

"I know Gingrich has a lot of baggage," Dyer said, in a reference to the attack ads that have pushed Newt Gingrich down in Iowa polls. "But do we need to know everything?"

Negative ads aren't new in politics, but the stealthy way they can be paid for is. This is the first presidential election that will be contested under the U.S. Supreme Court's 2010 ruling in the Citizens United case, which knocked down restrictions on political spending by corporations and wealthy individuals.

With their first-in-the-nation caucuses just days away, Iowa voters are getting a firsthand look at the new era of political ads funded not only by candidates and their parties, but by well-financed hybrid groups called Super PACs whose sources of funding won't likely be known until well after Iowans and voters in some other states have made their decisions.

Some fear the GOP primary race might be all but over before the money can be traced. The first disclosure deadline for donations to the Super PACs involved in the late stages of the Iowa campaigns is Jan. 31, the date of the Florida primary.

By then, voters in Iowa, New Hampshire and Nevada will have already cast their ballots.

"Voters are not going to have timely information on who is providing money to fund these expensive advertising campaigns," said Fred Wertheimer, president and CEO of Democracy 21, a campaign watchdog group in Washington, D.C.

But to David Bossie, president of Citizens United, what voters are seeing is unbridled democracy in action. "Throughout this presidential nominating contest we've seen enthusiastic supporters of the various candidates form Super PACs in support of their chosen candidates," he said. "Their independent speech has helped inform the voters and better enabled them to select the Republican nominee."

There's little argument from anyone that the new Super PACs, which can collect unlimited contributions from wealthy donors, have been a muscular presence in Iowa. Despite the caucus system's Norman Rockwell image of neighborly persuasion, an estimated $12.5 million has been spent on ads in Iowa so far by the candidates and independent groups supporting them.

Most talked-about ads

"The big story of 2012 is going to be the role that [independent] groups play in advertising," said Kenneth Goldstein, president of Kantar Media's Campaign Media Analysis Group, which tracks political advertising nationwide. "If you think of the big pie of advertising, parties are going to be less, candidates might be a little bit less, and the group piece of the pie is going to be bigger."

In Iowa, the most talked-about ads have been those aimed at Gingrich, the former House speaker vying with Mitt Romney and Ron Paul for supremacy in the GOP primaries. One of the big players is a Super PAC called Restore Our Future, whose ads slam Gingrich for his personal and political "mistakes." While the organization has ties to former Romney aides, campaign finance regulations prevent them from coordinating with Romney's campaign.

That has enabled Romney to distance himself from the ads, which have been criticized by Gingrich, who lacks the money to effectively fight back.

Rick Perry and Ron Paul and their supporters also have been spending heavily in Iowa, with Gingrich, Rick Santorum and Minnesota Rep. Michele Bachmann just starting to join the air campaign.

The result has been a buzz of conflicting messages on radio and television that have left many potential voters reaching for their remotes and changing channels.

"You just can't get away from them," said Des Moines office worker Jerad Huber, eating lunch Friday in a downtown restaurant with a flickering TV console displaying a series of noon-hour political ads.

Others object mainly to the negative tone of the ads run by the Super PACs and other outside interest groups that tend to do the dirty work for the candidates they support.

"At a certain point, they start slinging the mud, and that's when it becomes ridiculous to me," said Alesia Stone, manager of a Pizza Ranch restaurant in Indianola that has hosted personal visits from Bachmann, Paul and Gingrich.

There's also been talk of overkill.

"The TV stations are stacking them up four and five deep," said David Yepsen, former political reporter for the Des Moines Register and now director of the Paul Simon Public Policy Institute at Southern Illinois University. "When you get that level of saturation, especially during the holiday season, it starts to become Muzak -- just background noise, and none of it punches through."

'Tooth and nail'

Despite the objections, there is certainly evidence that negative ads work. Gingrich, a former Iowa poll leader, has lamented the role of negative advertising in driving down his support following a withering barrage of ads against him by forces allied to Paul and Romney.

Rick Santorum, who has been gaining in the polls, has been on the receiving end of Perry radio ads taking him to task for pork-barrel earmarks he supported in Congress.

One candidate who has largely remained out of the fray is Bachmann, whose low standing in the polls has inoculated her against attack. Nor does she have the money or the Super PAC support to participate, freeing her to take the high road of the underdog.

"We've purposely been making a decision about that," she told supporters at a cafe in Winterset this week. "Because the ads that are on TV right now are ripping the candidates apart tooth and nail, and they're welcome to do that."

Bachmann, however, sent ripples through the GOP field in November with an aggressive Web video ripping all the other GOP candidates in one 60-second spot dubbed "No Surprises."

One Super PAC that was once thought to be in Bachmann's camp, a group called Citizens for a Working America, has instead begun buying ads in Iowa to support Romney.

While President Obama and a host of liberal groups have criticized Citizens United for unleashing the power of big-money ad donors, conservatives see it as part of the continuum of money in politics.

"Even if you didn't have Citizens United, we'd be seeing other ways to bring money into the race," said Peter Nelson of the Center of the American Experiment, a conservative think tank in Minneapolis. "This is just a different route to funnel your money."

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