At least $12.5 million and counting has blanketed the airwaves ahead of next Tuesday's Republican presidential caucuses, with hard-hitting commercials awash in ghoulish images and startling claims. Most are coming from a proliferation of new independent groups aligned with the candidates.

To hear the ads tell it, Newt Gingrich is a "serial hypocrite," Rick Perry "double dips" as governor and the "liberal Republican establishment" is plotting to anoint Mitt Romney as the party's presidential nominee. The attacks, the bulk of the commercials on the air, reflected the volatile state of the race five days before the first votes of the GOP presidential nominating contest.

After a slow start, the ads in Iowa are coming on fast and furious.

Yesterday alone, at least five new commercials were rolled out, including one by Perry castigating his rivals as Washington insiders and saying: "The fox guarding the henhouse is like asking a congressman to fix Washington: bad idea." An outside group aligned with Romney, Restore Our Future, rolled out a new spot that criticizes Gingrich and asks: "Haven't we had enough mistakes?"

In the final days of the Iowa campaign, most of the ads are deeply negative, thanks in large part to the proliferation of outside groups, known as super PACs, that are doing the dirty work for candidates they support. Gingrich has been the biggest target, withering under attacks from Ron Paul's and Rick Perry's campaign as well as from several outside groups like the one aligned with Romney. Polls show that Gingrich's standing in Iowa has slid accordingly.

Gingrich, for his part, has railed against the Romney allies' ad blitz but has refused to respond in kind. A pro-Gingrich super PAC has begun fighting back, running ads in Iowa claiming the Republican establishment is "attacking him with falsehoods."

The ad warns: "Don't let the liberal Republican establishment pick our candidate."

"I call it ad wars whack-a-mole - this endless attacking in all directions, trying to slam down anyone who is surging to the top," said David Perlmutter, a University of Iowa journalism professor who studies political communication. "This is the most negative I've ever seen it. The ads are so blatantly negative I would have told you 10 years ago this would never fly in Iowa."

It's a different landscape in the campaign advertising world than four years ago when Barack Obama won Iowa's Democratic caucuses and Mike Huckabee carried the Republican side. Social media have intensified the advertising binge, with many spots debuting on TV but also going viral across the web at almost no cost to the campaigns that sponsor them. Candidates are making heavy use of online advertising to target voters based on location and other demographic information. Campaigns are also producing video specifically for the YouTube audience