South Carolina votes in primary
Republicans Mitt Romney and Newt Gingrich campaigned for every last vote in South Carolina before polls closed in a closely contested high-stakes primary battle that could shape the race to choose a Republican challenger to US President Barack Obama.
Mr Romney is fighting a suddenly surging Mr Gingrich, while rivals Rick Santorum and Ron Paul look to surprise in a four-man race that has spun wildly in its last 48 hours.
The first contest without Texas governor Rick Perry, who dropped out during the week and endorsed Mr Gingrich, was seen as Mr Romney's to lose just days ago. Instead, the gap closed quickly between the former Massachusetts governor who portrays himself as the Republican best positioned to defeat Mr Obama, and Mr Gingrich, the confrontational former speaker of the House of Representatives and ex-congressman from the neighbouring state of Georgia.
Mr Romney, Mr Gingrich and Mr Santorum, a former Pennsylvania senator, campaigned in South Carolina's conservative upstate as the voting got under way. Mr Paul, the libertarian-leaning Texas congressman who has campaigned lightly here, had no campaign appearances scheduled but was expected to visit campaign volunteers.
The stakes were high for the vote. The South Carolina primary winner has gone on to win the Republican nomination in every election since 1980 when Ronald Reagan was the victor. South Carolina voters were faced with stamping Mr Romney, who has led in national polls since December, as the party's front-runner, or reshuffle the contest yet again.
A victory by Mr Romney would place him in a commanding position heading into the next primary in Florida on January 31. Mr Romney had a big victory in the New Hampshire primary and a near-tie in the first nominating contest, the Iowa caucuses.
But if Mr Romney stumbles in South Carolina it could mean a battle for the nomination stretching over months that would further expose rifts inside the party between those who want a candidate who can defeat Mr Obama more than anything else, and those whose strong preference is for a solid conservative.
Mr Romney's agreement to participate in Florida debates on Monday in Tampa and on Thursday in Jacksonville was seen as an acknowledgement of a prolonged battle with Mr Gingrich. "This could be real close," said Mr Romney as he chatted on the phone with a South Carolina voter on Saturday morning and urged the man to vote.
Whatever the outcome, Mr Romney still has significant advantages over his three remaining Republican rivals, including an enormous financial edge and a well-organised campaign.
Mr Romney has struggled in recent days with questions about his personal wealth and taxes, while Mr Gingrich has been surging in polls after a pair of strong debate performances that appealed to the Republican base.