DES MOINES (AFP) - US presidential candidates made a frenzied, final push on Sunday to lock in Iowa voters on the eve of the first nominating contest of the 2016 election season.
Republican Donald Trump and Democrat Hillary Clinton both were leading in the polls, but not by enough to assure victory for either candidate in Monday's caucuses.
Armies of volunteers fanned out through the snow-swept Midwestern state, knocking on doors or manning phone banks to get out the vote, while candidates dominated the air waves.
Clinton, fearful of a repeat of 2008, when she was beaten to the punch in Iowa by an upstart Barack Obama, was leaving nothing to chance, stumping in the heartland this weekend as her main rival Senator Bernie Sanders did the same, seeking to deny her another shot at history.
A Bloomberg/Des Moines Register poll published late Saturday - the final one of the campaign - put Clinton just ahead of Sanders, 45 to 42 per cent, with a four percent margin of error.
The same poll gave Trump a bigger lead over his Republican rivals: The billionaire businessman had the support of 28 percent of voters, followed by Senator Ted Cruz at 23 percent, and Senator Marco Rubio with 15 percent.
"This race is as tight as can be," David Axelrod, President Obama's former political strategist, told The Des Moines Register.
Sanders has energized young Democrats with his denunciations of the "billionaire class" and his calls for a political revolution.
If the thousands of students who fill his rallies turn out on Monday they could produce an upset.
"If the turnout is high I think we've got a real shot to win this," Sanders told CNN's State of the Union program.
The Sanders campaign said it raised more than $20 million in January, nearly doubling its previous fundraising pace and underscoring an ability to stay in the US race for the longer haul.
The Clinton team has yet to release January numbers.
In the Republican camp, Trump and Cruz made appeals to Iowa's many evangelical conservatives.
Cruz said he was praying for his rivals as he worshipped at an evangelical mega-church in West Des Moines. He told reporters he had prayed that "God's blessing and peace and love be upon them." And long-shot hopefuls like Carly Fiorina reminded voters that polls are notoriously unreliable in Iowa, where political upsets are commonplace.
The three Democrats and 12 Republican candidates were hosting several dozen events as they geared up for Monday's vote.
The state is not large and is relatively homogeneous, but it is immensely consequential for the top finishers, who can claim momentum heading into the February 9 primary in New Hampshire.
On the Republican side frontrunner Trump has been tearing up the traditional playbook, largely avoiding the retail politics that require candidates to put in weeks in Iowa.
But he made the requisite appeal to evangelicals, who are expected to play a huge role on Monday - they comprised 57 percent of caucus voters in 2012.
Trump posted a short video on Facebook showing him holding up a Bible given to him by his mother, and assuring evangelicals, "I will never let you down." He displayed his usual confidence at a rally Saturday, declaring, "If we win Iowa, we can run the table!" But like other candidates Trump moved to soften expectations, telling CBS's Face the Nation, "I don't have to win it," even if "it would be really good." Cruz, locked in a do-or-die battle with Trump, is counting on a strong evangelical turnout to propel him to victory in Iowa.
"We need godly wisdom back in the White House," supporter Pam Cobb said at a Cruz rally in tiny Ida Grove.
Hovering in third place among Republicans is Rubio, whose star is seen as rising perhaps just at the right time.
"You have a right to be angry," the Florida senator told a crowd in Ames. "But anger is not a plan," he added, in a dig at the bombastic Trump.
Clinton took the stage at Iowa State University in Ames with her daughter Chelsea, along with former congresswoman Gabby Giffords, a shooting victim and advocate of gun control.
"Hillary is tough," Giffords said, by way of introduction. "She will stand up to the gun lobby." Sanders, for his part, held a raucous rally Saturday in Iowa City with rockers Vampire Weekend, underlining his popularity with younger voters.
"I believe it would be powerful to have a woman president," said a young Corinne Fonteyne, before adding, "but Bernie is the way I go."