DES MOINES, Iowa - Throwing elbows to the end, Republican candidates jostled over their conservative credentials and appealed to Iowa residents who were casting the first votes of the 2012 presidential race on Tuesday for a strong send-off into the long campaign season ahead.
Mitt Romney, a confident-but-cautious front-runner for the GOP nomination, looked past his Republican rivals to President Barack Obama in his final pitch to voters.
"This has been a failed presidency," he told voters in a Des Moines ballroom. "I will go to work to get Americans back to work."
With large numbers of likely caucus-goers still undecided or willing to change their minds, the outcome in Iowa was uncertain right up to the finish line in a race that has elevated and then discarded a head-snapping assortment of front-runners.
The two who appeared most likely to challenge Romney for victory in Iowa were former Pennsylvania Sen. Rick Santorum and libertarian Rep. Ron Paul of Texas -- neither of whom is likely to present as serious a challenge to Romney over the long haul as would former House speaker Newt Gingrich or Texas Gov. Rick Perry.
"It might come down to the speeches at the caucuses," said Phil Ubben, of Sioux City. "I want to support someone who can go all the way and defeat the Democrats in November."
The candidates pinned their final hopes on such voters.
Tuesday, CBS News correspondent Norah O'Donnell asked Gingrich: "You don't expect that you'll get first or second place, do you, Mr. Speaker?"
"Actually, I don't think anybody knows who is going to get what right now," he said
Referencing a Des Moines Register poll that said 41 percent of the voters were up for grabs, Gingrich said: "I think what you're seeing, and this has been our experience in all of our meetings over the last two - we have been in 24 towns by this afternoon when I go back to Waterloo - everywhere we go there are a large number of undecided people who walk in genuinely interested and tell you up front they haven't made their mind up. I think anybody could come in first."
Training their sights on the pack leader, Gingrich, Santorum and other GOP rivals questioned Romney's conservative convictions and predicted Obama would, to use Gingrich's words, "tear him apart."
Santorum, appearing on ABC's "Good Morning America," said Iowans are "looking for the candidate they can trust, and that's why we're moving up in the polls."
On Tuesday night, Republicans will gather in living rooms, high school gymnasiums and local libraries for caucuses that start the process of picking the GOP nominee. In each precinct caucus, voters will urge their friends and neighbors to support a preferred candidate. For all of the attention paid to the caucuses, they are essentially a nonbinding straw poll that awards no delegates. Republicans do that at county and district conventions later in the year.
Twenty-five delegates are at stake in Iowa, out of 1,144 needed to win the Republican nomination -- what Romney called "the whole enchilada."
Obama isn't ceding the stage to the Republicans while they sort that out: The president, fresh off a 10-day Hawaiian vacation, made plans to host an evening web chat with supporters in Iowa as the caucuses were under way.
And Mitch Stewart, a top Obama campaign aide, said in a morning email to the president's supporters: "Most of us will watch what happens on TV -- but, as you do, remember that the end of this story is up to you."
For all the talk of trust and electability, candidates in both parties know the economy is sure to be the central issue this election year: Obama was traveling to Cleveland on Wednesday for an event focused on the economy. Romney, for his part, said he's running to get the country back on track after Obama's mistakes.
Most polls in recent days have put Romney and Paul atop the GOP field in Iowa, with Santorum in third and gaining ground. More than a third of all potential caucus-goers said they could yet change their minds. Perry, Gingrich and Minnesota Rep. Michele Bachmann all trailed.
Romney faces the same challenge he did in 2008: winning over a conservative base that's uncomfortable with his moderate past. In 2008, socially conservative voters united behind former Arkansas Gov. Mike Huckabee, denying Romney a first-place finish and contributing to his eventual defeat.
Romney's 2012 rivals kept up their questions about his conservative convictions. Perry, speaking to Fox News Channel on Tuesday, dismissed Romney as a "conservative of convenience." Bachmann offered herself as the "one true conservative."
In the CBS interview, Gingrich called Romney a liar who would mislead the American people if elected as president -- yet he would still support Romney if the latter gets the GOP nomination.
"This is a man whose staff created the PAC," Gingrich said of Romney, "his millionaire friends fund the PAC, he pretends he has nothing to do with the PAC - it's baloney. He's not telling the American people the truth."
He added: "I just think he ought to be honest with the American people and try to win as the real Mitt Romney, not try to invent a poll-driven, consultant-guided version that goes around with talking points, and I think he ought to be candid. I don't think he's being candid and that will be a major issue. From here on out from the rest of this campaign, the country has to decide: Do you really want a Massachusetts moderate who won't level with you to run against Barack Obama who, frankly, will just tear him apart? He will not survive against the Obama machine."
Emotions -- and rhetoric -- were hot in the campaign's final hours.
Santorum, blaming the Paul campaign for recorded phone calls questioning his policies on guns and abortion, told reporters at Fox News that "Ron Paul is disgusting."
Romney said he can handle any criticism his Republican rivals heap on him, calling it only a warm-up to whatever will come from Obama's camp. "My shoulders are wide," he insisted on Fox.
This time, Romney's trying to win Iowa by arguing he's the most electable candidate against Obama -- a pitch that's winning over conservatives who desperately want to beat the president.
"I want to make sure I vote for and caucus for someone who is a winner. We cannot have another four years of Obama," said eyeglass salesman Paul Massey, 65.
How many people turn out to vote will help drive the results. In 2008, more than 120,000 Republicans showed up, a record. Weather could be a factor this year. Iowa hasn't had much snow this winter, and there were clear but cold forecasts across the state.
After Tuesday's vote, Romney, Gingrich and Santorum planned to depart immediately for New Hampshire. Romney holds a commanding lead in polls there, and will be in a strong position to win even if he doesn't pull out a victory in Iowa. Paul plans to join his rivals in New Hampshire later in the week. The primary is Jan. 10.
Perry and Bachmann, both short-lived front-runners, don't plan to compete in New Hampshire, instead heading straight from Iowa to the first-in-the-South primary, set for Jan. 21 in South Carolina. Bachmann pronounced herself ready to move on: "This election is far from over," she said. "This is the opening chapter. Tonight is the first vote. We've got a long road to go."
Perry tried to buck up disheartened supporters by comparing caucus day to historic military campaigns of yore: "This is Concord," he said. "This is Omaha Beach."
Romney also plans to visit South Carolina this week, with campaign stops Thursday and Friday.