(CNN) - Super PACs have spent $35.4 million on the 2012 presidential race, according to federal campaign disclosures, including $11.4 million on last Saturday's South Carolina Republican primary and $6.4 million on next week's contest in Florida.
More than half of the spending by these political organizations has focused on the ongoing war of words between supporters of leading GOP presidential candidates Mitt Romney and Newt Gingrich. Restore Our Future, a group supporting Romney, has spent $11.7 million, compared to $7.7 million for Winning Our Future, a group that supports Gingrich.
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An overwhelming majority of the two groups' spending has been in opposition to the other candidate, rather than in support of their own. The pro-Romney super PAC has spent 92% of its expenditures attacking Gingrich, while 79% of the pro-Gingrich group's spending has focused on attacking Romney.
Gingrich continues to be the most popular target of super PAC attacks. Groups, primarily Restoring Our Future, have spent $10.8 million attacking him, while Romney has been the target of $7.5 million worth of attacks.
Conservative super PACs have spent more than $600,000 attacking President Obama over the past year in anticipation of the general election contest. Similarly, Democratic-leaning groups have also weighed in on the Republican presidential primary contest. The labor union AFSCME reported spending $1 million last week on a TV ad buy in Florida attacking Romney.
Super PACs, which were created following a pair of federal court decisions in 2010, are permitted to receive unlimited campaign contributions from corporations, labor unions, and wealthy individual donors. Traditional federal political action committees and candidate campaign committees may only receive limited contributions from individuals, political parties, and other political action committees. Under federal law, candidates and super PACs are not permitted to coordinate campaign activity.