Gingrich wins South Carolina primary

Newt Gingrich has stormed to an upset victory over Mitt Romney in the South Carolina GOP primary with a pair of strong debate performances that most voters said was important to their choice.

Within minutes, the former speaker of the House was looking ahead to the next contest Jan. 31.

"Thank you South Carolina!," he tweeted. "Help me deliver the knockout punch in Florida."

In exit polls, most voters said they made up their minds in the last few days of the campaign. Two-thirds said the debates were an important factor in their vote.

Gingrich led among the state's conservatives, tea party supporters and born-again Christians. Romney held a small advantage among moderate and liberal voters, and those who are not born-again Christians.

Gingrich, the former House speaker, has won at least 15 delegates, with 10 to be awarded. These are the first delegates Gingrich has won in a primary or caucus, though the race for delegates is still in the early stages.

In all, Gingrich has 17 delegates, including endorsements from Republican National Committee members who will automatically attend the convention. Romney has 33 delegates.

It will take 1,144 delegates to win the GOP nomination.