Updated 7:36 p.m. Eastern Time
Newt Gingrich has defeated Mitt Romney in the South Carolina Republican primary, CBS News is projecting from analysis based on exit polls and early vote totals. Rick Santorum and Ron Paul are battling for third place.
"Thank you South Carolina!" Gingrich tweeted as CBS News and other news outlets projected his victory.
Gingrich's victory ends Romney's hopes of effectively wrapping up the GOP presidential nomination by the end of the month - and breaths new life into Gingrich's campaign ahead of the Florida primary on January 31. South Carolina has voted for the candidate who went on to with the GOP nomination in every primary since 1980.
Gingrich's win was due in large part to his strong performance in two debates in the state this week. Nearly two in three GOP primary voters said the debates played an important role in their decision, and more than half (53 percent) made up their minds in the last few days, according to exit poll data.
Among these late-deciders, Gingrich was the clear favorite: 45 percent backed him, compared to 24 percent for Romney and 19 percent for Rick Santorum. And among the 64 percent who said the debates were an important factor, 50 percent backed Gingrich, while just 23 percent were backing Romney. FULL STORY