4.54pm: With 88% of the vote in, only 50 votes are separating Romney and Santorum -- 26,443 for Santorum, 26,398 for Romney. This could be the closest results Iowa's ever seen, a clear tussle between the highly conservative right wing and the more pragmatic Republicans.
4.50pm: With 60% of the vote in, Santorum is leading with 25% of the vote, pulling away from Romney with 23.2%. Many are probably asking now, who is Rick Santorum? The 53-year-old former Pennsylvania senator is derided by liberal opponents as an ultra-religious, anti-gay creationist who in the past has equated homosexuality with incest and pedophilia but Santorum plays his social and fiscal conservatism as trump cards. Just this week, he's said if he's elected president, he would bomb Iran's nuclear facilities unless they were opened up for international arms inspectors.
4.30pm: With 50% of the vote in, it's still a tight race but now long-shot candidate Rick Santorum is ahead with 24.3% of the vote, with Romney at 23.6% and Paul at the rear with 21.8%.
4.20pm: Candidates at the rear such as Gingrich can take heart -- Iowa has an uneven record when it comes to predicting national winners. It sent Obama on his way in 2008, but eventual Republican nominee John McCain finished a distant fourth here to former Arkansas Gov. Mike Huckabee. The 100,000 or so voters are disproportionately white and more conservative than the overall American electorate. Still, a victory means a wave of publicity, a likely boost in campaign contributions and a guarantee of surviving for at least a few more contests. Candidates who do poorly may feel compelled to drop out of the race.
4.00pm: Less than 200 votes separate Romney, Santorum and Paul with 31% of the vote counted. Romney is holding on a narrow lead with 7,844, Santorum 7,726, and Paul 7,655. The other candidates are far behind.
3.55pm: He won Iowa four years ago and that jump-started his campaign for the White House, but US President Barack Obama is keeping a low profile in today's event. Obama was unopposed for his party's nomination. His re-election campaign set up eight offices across Iowa, made hundreds of thousands of calls to voters and arranged a video conference with caucus night supporters. "This time out is going to be in some ways more important than the first time,'' Obama told Democrats across the state. "Change is never easy.''
3.43pm: She was the candidate who won a "straw poll" in Iowa and a whole bunch of publicity as a result, but Michelle Bachmann is running dead last so far in the caucuses tonight with less than 6 percent of the vote. Expect talk about her leaving the race soon if the results keep up.
3.32pm: Just seven votes separate Santorum and Romney, with a quarter of the returns in, while Paul has slipped back to third place, but is only about 40 votes behind. All three men have just over 6000 votes, and 23 per cent of the total.
3.20pm: with 18 per cent of the returns in, Paul has a slim lead with 24 per cent of the votes counted so far, followed closely by Santorum on 23.2 per cent and Romney on 22.6 per cent.
3.05pm: The first fragmentary returns according to the Associated Press, from 49 of 1,774 precincts, showed Santorum with 26 percent of the votes, Paul with 23 percent and Romney with 18. Gingrich had 16 percent, followed by Perry with 10 percent and Bachmann with 6 percent.
2.55pm: An entrance poll of early arriving caucus-goers in Iowa suggests that former Massachusetts Gov. Mitt Romney, Texas congressman Ron Paul and former Pennsylvania Sen. Rick Santorum are in the top tier of vote-getters in the Republican presidential contest.
The other candidates in the race are former House Speaker Newt Gingrich, Minnesota congresswoman Michele Bachmann and Texas Gov. Rick Perry.
The survey by Edison Media Research for The Associated Press and television networks was based on interviews with more than 600 people arriving at nearly 40 precinct caucuses across the state.
