A confident Mitt Romney looked to seize the momentum in the Republican presidential race with a victory in Tuesday's lead-off Iowa caucuses, but his rivals worked to undermine the perception that he was the candidate best positioned to defeat President Barack Obama.
The final Des Moines Register poll showed the former Massachusetts governor and Texas Representative Ron Paul locked in a close race in Iowa, with former Pennsylvania Senator Rick Santorum rising swiftly to challenge them.
Nearly half of likely Iowa caucus-goers view Mr Romney as the Republican most likely to win the November general election. He was far ahead of Mr Santorum and Mr Paul in this regard.
With Mr Romney in a position of strength in Iowa, both Mr Santorum and Mr Paul went directly at Romney's chief argument - that he is the most electable Republican in a head-to-head match-up against Mr Obama next autumn.
They hope they can sway the roughly half of likely caucus-goers who say they are undecided or willing to change their minds two days before Iowa begins the state-by-state nominating contests spread over the next six months.
Only three or four candidates typically make it out of Iowa with enough momentum and money to continue in the race.
Mr Paul and Mr Santorum were fighting against the notion in Republican circles that their bases of support are narrow and neither would be able to cobble together the diverse voting coalition necessary to beat Mr Obama in November.
The libertarian-leaning Mr Paul attracts legions of backers who like his message of states' rights and limited central government, while Mr Santorum - an anti-abortion crusader - is popular among Christian conservatives who make up a large segment of the Republican Party base.
In contrast, Mr Romney has styled himself as a Republican able to attract a broad spectrum of voters. As polls showed him with a narrow lead in Iowa in the past week, he has redoubled his effort to portray himself as the business-savvy executive with national appeal who is best able to challenge Mr Obama on the campaign's most pressing issue, the economy.
Polls show Mr Obama is vulnerable as he seeks a second term, weighed down with voter dissatisfaction over the sputtering recovery from the Great Recession.