LOVELAND, Colo. (Reuters) - Republican candidate Rick Santorum is gunning for a victory in at least one of the three states holding presidential nominating contests on Tuesday in a bid to slow front-runner Mitt Romney and revive his fading White House hopes.
The former senator from Pennsylvania narrowly won Iowa's caucuses on January 3 but his drive to become the main conservative alternative to the more moderate Romney has not played out the way he had hoped.
He has had weak showings in New Hampshire, South Carolina, Florida and Nevada, the states that have voted since Iowa.
Tuesday may give Santorum a modest boost. Colorado and Minnesota hold Republican caucuses in the state-by-state battle to decide on the party's challenger to Democratic President Barack Obama in the November 6 presidential election. Missouri holds what amounts to a non-binding "beauty contest."
Pollsters said Santorum was leading in Minnesota and was second to Romney in Colorado.
Santorum has made his strong positions on social issues a centerpiece of his campaign and is hoping that his staunch opposition to gay marriage and abortion will help win over religious conservative voters in upcoming nominating contests.
Many Christian conservatives are wary of Romney because of moderate positions he took while running for office in Democratic-leaning Massachusetts. This has kept divisive social issues like abortion on candidates' radar in a 2012 contest that had been expected to center on the struggling U.S. economy.
Romney took aim at Obama over religion for a second straight day on Tuesday. He sharply criticized two moves by the Obama administration that he said amounted to an "assault on religion."
One involved the Obama administration's argument against providing ministers an exemption from anti-discrimination laws. The Supreme Court ruled 9-0 in January for the exemption. The other was a decision to force Roman Catholic hospitals and schools to provide employees medical insurance that covers contraceptives.
"This kind of assault on religion will end if I am president of the United States," Romney said.
The Obama administration has been signaling some flexibility on such issues.
A top adviser to Obama's re-election campaign said on Tuesday the administration was willing to work with Catholic universities and hospitals in implementing rules that require health insurance to cover birth control.
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A victory on Tuesday would revive Santorum's hopes and enable him to make the case to fundraisers that his campaign remains viable. And, it would allow him to compete with former House of Representatives Speaker Newt Gingrich as the main alternative to Romney.
A Reuters/Ipsos poll showed that Santorum's support has grown by 5 percentage points among Republicans nationally in the past month. In the new poll conducted February 2-6, his backing was at 18 percent, versus 13 percent a month earlier.
The poll put Santorum in a virtual tie with Gingrich, at 19 percent, and Paul, at 21 percent, with the gap between them within the poll's margin of error, but all three still significantly behind Romney's 29 percent.
Fund-raising is crucial in an election expected to be the most expensive in U.S. history and in which outside fund-raising groups known as Super PACs, thanks to a controversial 2010 U.S. Supreme Court ruling, are playing a huge part.
Santorum trails far behind in the fund-raising stakes.
Obama's campaign, in a reversal, said late on Monday it would start supporting the struggling Super PAC designed to help Obama stay in office. A Romney aligned Super PAC, "Restore our Future," had raised $30.2 million in 2011, versus $4.2 million for the pro-Obama "Priorities USA Action.
In a sign of his expectations, Santorum was scheduled to hold his caucus-night celebration in Missouri where he has a good chance. Gingrich is not even on the ballot. The vote there is symbolic because delegates will be won in mid-March in the binding portion of a two-step process.
Romney's party will be in Denver. He spent Monday and Tuesday campaigning in Colorado after winning the Nevada caucuses by a wide margin on Saturday.
His campaign acknowledged the race was close in Minnesota but believed the former Massachusetts governor could absorb a loss without a lot of damage.
Even so, Romney's campaign attempted to remind voters of Santorum's penchant for seeking hundreds of thousands of dollars in government grants for his home state when he was a senator, a practice conservatives see as wasteful spending.
Gingrich had no event scheduled in the states that were voting. He spent Tuesday campaigning in Ohio, which does not hold its primary until "Super Tuesday," March 6, when there are primaries and caucuses in 10 states. Early voting in Ohio's primary starts February 7.
Texas congressman Ron Paul spent Tuesday in Minnesota, where he was to hold an election event on Tuesday night. Paul finished third in Nevada and has yet to win a 2012 nominating contest.