Upset?

Santorum Leads Romney Nationally

Calls out Mitt for making "desperate" attacks.

Rick Santorum isn't just leading in Michigan. The onetime Pennsylvania senator, and former underdog, has pushed ahead to frontrunner status—taking 30 percent of registered Republican support, according to a new Pew Research Center poll. His closest competitor, Mitt Romney, has slipped from his position at the top of the GOP field and, the poll finds, is supported by 28 percent of registered Republicans. At this point, however, neither of the top GOP candidates is any match for President Obama, who has a 10-point lead over Santorum and an 8-point lead over Romney among all voters. Santorum has accused Romney of making "desperate" attacks against him. "Another candidate has come up to challenge him, and this time he's having trouble finding out how to go after someone who is a solid conservative, who's got a great track record of attracting independents and Democrats and winning states as a conservative," Santorum said on ABC's This Week.