CANTON, Ohio (AP) — Mitt Romney’s allies are hoping Super Tuesday’s powerful imprint on the Republican presidential nomination will bring clarity, at long last, to the fractious contest and rouse Republicans behind their front-runner. But that’s strictly up to voters across the nation, weighing in on the most consequential day of the campaign to date.

Romney and his chief rival, Rick Santorum, scrambled for any advantage they could find Monday in Ohio, the most-watched contest in the 10-state extravaganza stretching from Alaska to the southeast.

Speaking to supporters at a guardrail factory in Canton, Ohio, Romney tried to snap the subject back to the economy and away from social conservative issues — this, after a furor erupted from radio host Rush Limbaugh’s caustic comments about a college student who testified to Congress about contraception.

“I look at this campaign right now and I see a lot of folks all talking about lots of things, but what we need to talk about to defeat Barack Obama is getting good jobs and scaling back the size of government, and that’s what I do,” Romney said. “Other people in this race have debated about the economy, they’ve read about the economy, they’ve talked about it in subcommittee meetings. But I’ve actually been in it.”

The latest polls found Santorum slipping in Ohio, putting him in a near dead heat with Romney, and Gingrich looking strong but not invincible in his home state of Georgia, which he needs to win to have any hope of resurrecting his candidacy. Ron Paul, trailing the delegate count and the expectations game, hoped one or more of the three caucus states, Alaska, Idaho and North Dakota, would finally give him a victory.

Fully one-third of the delegates needed to clinch the nomination are at stake Tuesday, altogether a larger prize than all the previous primaries and caucuses combined. President Barack Obama picked Tuesday for his first news conference of the year, a chance to steal a bit of thunder from the Republicans on their big day and defend a record of economic stewardship that is under daily assault in the GOP campaign.

On the eve of Super Tuesday, the message coming from Republican establishment figures was clear: It’s time, if not past time, to crystallize the competition and unite the party behind the effort to defeat Obama in the fall.

House Majority Leader Eric Cantor of Virginia and Oklahoma Sen. Tom Coburn, one of the most conservative members of the Senate, were among the latest GOP luminaries to swing behind Romney. Conservative John Ashcroft, attorney general in the George W. Bush administration and a former Missouri senator, threw his support behind Romney on Monday. “No other candidate stands out for his executive leadership experience or ability to accomplish difficult task as does Mitt Romney,” he said.

Cantor told CNN “we’re coalescing around Mitt Romney’s plan to actually address the economic challenges,” and “trying to find ways to work together and bring people together and set aside differences.”

Whether Super Tuesday marks that sort of turning point remains to be seen. Romney has been the presumed long-haul favorite from the start but Santorum’s surge unfolded as the latest in a line of surprises from a field now down to four candidates.

Gingrich, whose only victory was in the Jan. 21 South Carolina primary, has staked his campaign’s future on winning Georgia, the state he represented in Congress for 20 years, and on building a stronghold in the conservative South.

Toward that end, Gingrich scheduled stops Monday in Tennessee, where he appears to be in a close race with Santorum and Romney. Gingrich also planned to visit Alabama on Tuesday for the state’s March 13 primary before returning to Atlanta in the evening.

Santorum told The Associated Press on Sunday that Romney’s inability to wrap up the nomination, despite an enormous financial advantage, “raises a lot of questions in people’s minds whether this is the man who can unite the party and be effective as a foil against Obama.”

He suggested that the GOP nomination may not be settled until the party convention in late August, a circumstance considered improbable despite the jumble so far.

While Romney has a significant advantage in northeastern states such as Vermont and Massachusetts — where he was governor — and Santorum is strong in conservative states such as Oklahoma, Ohio tops the list of hotly competitive and delegate-rich contests Tuesday. Both candidates focused on the state Monday after a weekend swing through the South.

Romney has been working to make the race about the economy and to avoid intensifying the debate over conservative social values, a strong suit for Santorum. That effort was not helped when Limbaugh called a Georgetown University law student a “slut” and a “prostitute” on his nationally syndicated radio program, later apologizing.

The woman had testified at a congressional hearing in favor of an Obama administration mandate that employee health plans include free contraceptive coverage.

Arizona Sen. John McCain, the 2008 Republican presidential nominee, denounced Limbaugh’s comments Monday, saying the remarks “should be condemned” by people across the political spectrum. The 2012 GOP candidates have dissociated themselves from Limbaugh’s comments, though not as forcefully as McCain did on CBS’ “This Morning.”

Romney has won four consecutive contests, including Saturday’s Washington caucuses. His broad, well-disciplined organization all but assures he’ll collect more delegates than his opponents on Tuesday, in contrast with Santorum’s looser group of supporters. Santorum and Gingrich did not collect enough signatures to qualify for the Virginia ballot, for example, and Santorum cannot win 18 of Ohio’s 66 delegates for similar reasons.

All told, 419 delegates are at stake Tuesday. Romney leads with 203 delegates from previous contests, Santorum has 92, Gingrich has 33 and Paul, 25. It takes 1,144 delegates to win the nomination.