The outcome of Republican primary and caucus votes in 10 states Tuesday offers Mitt Romney yet another chance to become the party's inevitable nominee to face President Barack Obama in November.

That will depend largely on the vote in the bellwether state of Ohio, where polls show the former Massachusetts governor and Rick Santorum, a former Pennsylvania senator, in a virtual tie.

Romney, who turned back Santorum in a close contest in Michigan last week, hoped to continue his winning trend, having won four consecutive contests including Saturday's Washington state caucuses.

At stake in the 10 states that cast ballots during what's known as Super Tuesday are 419 delegates to the party's August national convention, by far the most of any day in the primary season. A candidate must amass at least 1,144 to win the nomination.

Going into the Tuesday balloting, Romney leads with 203 delegates from previous contests, Santorum has 92, Newt Gingrich has 33 and Rep. Ron Paul, 25.

Romney, despite his lead, still faces persistent skepticism among conservative voters who dislike his past moderate record.

While a big chunk of vote was being cast Tuesday, the race was expected to continue further into March because delegates are apportioned based on vote percentage and the candidates are focusing on different regions.

Obama, meanwhile, is seeing his poll numbers rise in tandem with signs that the struggling US economy may finally be on a course toward sustained recovery. An Associated Press survey late last month of leading economists shows the economy is improving faster than had been expected, while an NBC-Wall Street Journal poll released Monday shows Obama defeating all Republican candidates in hypothetical head-to-head matchups.

Obama also has been helped considerably by the Republicans having been driven off their economic message by a detour into a nasty debate over whether religious-affiliated institutions such as hospitals and universities should be required to offer health insurance coverage for contraceptives.

And the issue seemed certain to deepen the concerns of many women voters, who, along with the broad spectrum of all independents, will likely determine the ultimate outcome in the November election. Polls show women are already turning back to Obama.

Obama picked Tuesday to hold his first news conference of the year, a chance to steal a bit of thunder from the Republicans and defend a record of economic stewardship that is under daily assault in the Republican campaign.

Priorities USA Action, a super Political Action Committee backing the president, trained its criticism solely on Romney, issuing a ``Super Tuesday memo'' to argue that the front-runner's ``agenda for the wealthy'' was hurting him with those who are not.

In the Republican race, a Romney loss to Santorum in Ohio almost certainly would assure that the primary contest continues further into March or perhaps beyond.

The focus on social issues has propelled the success of Santorum, who campaigns as a social conservative and is the latest candidate to pose a threat to Romney.

Having fallen behind Santorum in Ohio last month, Romney has closed the gap in recent days. It's a familiar trend for Romney, whose superior fundraising and turnout operation helped him turn deficits in Florida and Michigan into victories.

Third-place Newt Gingrich, the former speaker of the House of Representatives, has focused his efforts on Georgia, the state that he represented in Congress for two decades. Georgia is part of Gingrich's strategy to reinvigorate his once top-tier candidacy by sweeping primaries in the American south.

At a breakfast meeting of a suburban Atlanta chamber of commerce, Gingrich criticized his rivals as mere managers, rather than leaders of the change he recommends.

``The truth is I have opponents who are, in a normal period, adequate,'' he said. ``But they don't have anything on the scale of change I just described to you.''

Paul, who holds a small but loyal bloc of voters who favor his small-government, low-tax libertarian message, has focused on the smaller states that vote at caucus meetings that are easier to win in for a low budget candidacy like his.

Romney projected confidence ahead of the Tuesday vote. ``I hope that I get the support of people here in Ohio tomorrow, and in other states across the country. I believe if I do, I'll get the nomination,'' he said.

Romney, a former private equity firm executive, tried to keep his campaign's focus on the economy and away from divisive social issues in a final sprint across Ohio.

Romney is expected to do well in Massachusetts, where he served a four-year term as governor, and Vermont, a neighboring state. He is also poised to win the Virginia primary where Santorum and Gingrich did not collect enough signatures to qualify for the ballot.

Romney's broad, well-disciplined organization all but assures he'll collect more delegates than his opponents on Tuesday. Santorum cannot win 18 of Ohio's 66 delegates because he failed to qualify his delegate slates in several congressional districts.

Besides Ohio, Santorum is competing most aggressively in primaries in Oklahoma and Tennessee, where the Republican electorate's conservative hue matches his strict social conservative's appeal to religious voters. He was leading narrowly in Tennessee, where polls showed Gingrich and Romney closing.

Despite signs that Gingrich planned to remain in the race, Santorum urged voters in Ohio to see it as increasingly a two-candidate fight.

At a rally at Dayton Christian School, Santorum said that no matter how much Romney spends on his campaign, ``conservatives will not trust him, will not rally around him this primary season.'' He has cited Romney's past support for abortion rights and a health care reform plan enacted in Massachusetts that Obama used as a model in crafting his national program that Republicans loathe.

Romney turned to foreign affairs in an opinion piece published in Tuesday's editions of The Washington Post, writing that if he were president, he would combine diplomacy with ``a military option'' to stop Iran from acquiring nuclear weapons. He said he would increase military assistance to Israel.