Democrat Hillary Clinton holds a slim lead in Iowa over Barack Obama and a rising John Edwards, who are tied for second place three days before the state opens the presidential nominating race, according to a poll released today.
In the tight Republican contest in Iowa, Mike Huckabee narrowly leads Mitt Romney, who slipped by one point to trail 29 per cent to 27 per cent. John McCain gained two points but remained a distant third at 13 per cent.
About 6 per cent of likely caucus-goers in each party remain undecided of their choice in Thursday's contest, the first big test in the state-by-state battle to choose Republican and Democratic candidates in November's presidential election.
"It's about as close as you can get at the top in both races," pollster John Zogby said. "But it's still very uncertain."
The Reuters/C-SPAN/Zogby poll of 899 likely Democratic caucus-goers and 902 likely Republican caucus-goers was taken Thursday through Saturday and has a margin of error of 3.3 percentage points for each party.
Most of the top candidates in both parties have been crisscrossing Iowa for days in a late hunt for support that could give them an edge and momentum for later contests.
The poll showed Ms Clinton, a New York senator and former first lady, leading Mr Edwards and Illinois Sen Obama by four points, 30 per cent to 26 per cent. Mr Edwards, a former North Carolina senator, gained two points overnight to pull even with Mr Obama.
Delaware Senator Joseph Biden and New Mexico Governor Bill Richardson were at 5 per cent. Connecticut Senator Chris Dodd and Ohio Representative Dennis Kucinich were at 1 per cent.
The poll found Ms Clinton's supporters remained the most dedicated with 73 per cent saying their support was "very" strong, compared to 66 per cent for Mr Edwards and 63 per cent for Mr Obama.
Under Iowa's arcane caucus rules, candidates must receive support from 15 per cent of the participants in each precinct to be viable. If not, their supporters can switch to other candidates.
In the Republican race, Mr Huckabee held on to his slim two-point lead despite an Iowa ad campaign from Mr Romney attacking Mr Huckabee's record as governor of Arkansas.
Mr McCain solidified his hold on third with his two-point gain to 13 per cent. Three Republicans battled for fourth, with former Tennessee Senator Fred Thompson at 8 per cent and former New York Mayor Rudy Giuliani and Texas Representative Ron Paul at 7 per cent.
A third-place finish for Mr McCain, an Arizona senator who has largely bypassed Iowa to concentrate on the next contest in New Hampshire, would give him a small measure of momentum going into that state's January 8th primary.
Mr Romney, the former Massachusetts governor, has been running hard in both Iowa and New Hampshire. His top rivals in each state have concentrated on just one - Mr Huckabee in Iowa and Mr McCain in New Hampshire.