Study: Negative campaign ads much more frequent, vicious than in primaries past And the negative ads are not just more frequent - they also appear to be more vitriolic. In 2008, one of harshest ads Mitt Romney ran ahead of the Iowa caucuses criticized the immigration position of Sen. John McCain (R-Ariz.), but only after calling him "an honorable man." In 2012, such a nicety seems quaint. Romney's campaign began running an ad Friday in Michigan showing a limp body sinking in murky water, while a narrator intones: "America is drowning in national debt, yet Rick Santorum supported billions in earmarks." All of this invective is flowing in an election season when Republicans had hoped to train their resources on beating President Obama. Candidates typically save their harshest attacks for the general election, largely sparing their fellow party members. But a wildly unpredictable GOP primary has upended that plan and dissolved the truce. It is happening largely because of new rules governing campaign money. Also, this race has a different dynamic - a front-runner who lacks a prohibitive lead. Once the tone of the race turned negative, it stayed that way. One Ron Paul campaign ad calls Newt Gingrich a "serial hypocrite." Another spot, from a group backing Romney, asks, "Haven't we had enough mistakes" from Gingrich? A group backing Gingrich accused Romney of being a "corporate raider" and showed footage of an elderly woman saying, "I feel that is the man who destroyed us." Another spot from the group accuses Romney of making "blood money" from a company that was found guilty of bilking the government for Medicare payments. Romney and the groups backing him have led the trend, spending two-thirds of their money on negative ads. Gingrich and the Winning Our Future PAC backing him have spent half of their funds on spots attacking other Republicans. Santorum and the PACs behind him have devoted one out of four dollars to attack ads. Winning Our Future spokesman Rick Tyler said his group's message was positive until it was forced to counter Romney's "scorched earth" strategy. "When this whole campaign started, the Republicans were very enthusiastic," Tyler said. Romney's approach, he said, is also depressing turnout: "By the time he's done, there will be no one left to vote against Barack Obama." The Romney and Gingrich campaigns did not respond to requests for comment, and Restore Our Future, the largest super PAC supporting Romney, declined to comment. Party strategists point to million-dollar political contributions to super PACs as part of the reason for the negativity. Data show that super PACs, which have run more advertising than the campaigns themselves, have spent 72 percent of their money on negative ads. The figure for campaigns is 27 percent, according to a Washington Post analysis of data from Kantar Media/CMAG, which tracks television advertising across the country. For this article, ads were considered negative if they mentioned another GOP candidate.