Voters in Iowa begin the process of choosing the next US president tonight as Democrats Hillary Clinton, Barack Obama and John Edwards scramble for the top spot in the campaign's first nominating contest.
Iowa opens the state-by-state battle to choose candidates in the November election to succeed President George W. Bush, and traditionally has served to winnow the field of laggards and elevate some surprise contenders.
Polls show a tight race between Mitt Romney and Mike Huckabee for the Republican lead as the most heavily contested Iowa campaign in history draws to a close.
For the winner in Iowa, the prize is valuable momentum and at least a temporary claim to the front-runner's slot in their party's nomination battle.
US Democratic presidential candidate Senator Hillary Clinton speaks during a campaign rally in Des Moines, Iowa last night
But the third-place finisher in the Democratic showdown could find themselves severely wounded heading into the next contest in New Hampshire on Tuesday.
The 2008 campaign is the most wide open presidential race in more than 50 years, with no sitting president or vice president seeking their party's nomination.
A tracking poll found Ms Clinton's support in Iowa slipped slightly and Mr Obama's inched up yesterday, leaving them tied at 28 per cent among Democrats, with Mr Edwards just two points behind.
Mr Huckabee, the former Arkansas governor, led former Massachusetts Governor Romney by two points in the Republican race on the eve of the caucuses in Iowa , with Arizona Senator John McCain and former Tennessee Senator Fred Thompson tied for a distant third.