WILLOUGHBY, Ohio - This state's Super Tuesday primary is proving to be the perfect microcosm of the nation's unruly race for the Republican presidential nomination: Mitt Romney is spending lots of money, Rick Santorum is aggressively courting conservatives and Newt Gingrich is counting on big ideas to swing votes his way.

Of the 10 states weighing in on Tuesday, Ohio offers the hottest contest. And with its diverse population, reputation as a presidential battleground and preoccupation with the same economic worries that nag the nation at large, Ohio seems destined to foreshadow the shape of the campaign as it heads toward November.

"You seem to always be the center of the political universe in America," Santorum declared Friday night during a packed campaign stop in this northeastern Ohio town set along Lake Erie.

And despite the vast territory in play across the country, from Alaska and Idaho to Vermont, Virginia and Georgia, Romney will sleep in Ohio every night until Tuesday. It's that important to him.

Even so, the race was playing out in similar fashion in the other states with contests Tuesday. The former Massachusetts governor and his allies were flooding the airwaves, outpacing his rivals in every Super Tuesday state except in North Dakota, where Santorum was alone on the air but spending less than $8,000. Romney campaigned in Washington on Friday, the day before the state's caucuses, as he closed a Western swing.

Romney has much of Ohio's Republican establishment behind him after years of courting the party's county chairmen and donors.

"When a party chairman gets a call early on from someone perceived as the front-runner and they ask you to sign on as a county chairman, it's easy to say yes and it's hard to say no," said Mark Munroe, the Mahoning County GOP chief who is leading Romney's efforts in the northeastern Ohio county. "We've seen the Romney campaign in action since late last year. He was able to start early and that makes such a huge difference."

Romney's camp insists he does not need to win Ohio to get the presidential nomination or even to keep alive the expectation that he eventually will. Losing here, however, would drive persistent doubts about the strength of Romney's candidacy after a closer-than-expected race in Michigan and a string of comments that have drawn attention to his personal wealth.

Campaigning Friday night in Cleveland, Romney delivered his standard speech and kept his focus on the economy, though he cited trade - a critical issue in a manufacturing state that's been hurt by foreign competition

"When we have trade with other nations it's good for us ... we do better as a society. We're able to have more stuff and have a more prosperous life," he said. "But that's only the case as long as the people we trade with don't cheat. And in the case of China, they're cheating." The crowd cheered, with many nodding their heads.

Romney, who's visited Ohio, North Dakota, Idaho and Washington state in the past two days, also said the campaigning allows him to meet people who aren't regularly in the news. "When you get to do what I do and you meet, you know, average, ordinary citizens like ourselves, well, you get a sense of what is really at the heart and at the core of the American people," he said.

Figures provided to The Associated Press show Romney's campaign is spending more than $1.5 million in television ads this week in Ohio and his allies are on the air with almost $1.5 million. In total, Romney and his supporters planned to spend more than $3.8 million on cable and broadcast television ads.

His rivals dismiss the spending.

"The Romney organization is nothing more than money," said Ohio Attorney General Mike DeWine, an early Romney backer who defected to Santorum just as the former Pennsylvania senator's late rise captured the interest of conservative leaders who were lukewarm, at best, about Romney's record.

Santorum and his allies are spending only $796,000 in total on Ohio. Yet a Quinnipiac University poll released Friday found Santorum polling at 35 percent support and Romney at 31 percent support - essentially a tie.

"When Ohio whispers, people listen," Santorum said Friday night. "When Ohio shouts, 'We want a conservative,' this country will stand up and join you."

Ohio's Republican electorate is similar to that of the most recent hard-fought state, Michigan, containing both blue-collar, rural voters as well as churchgoers focused heavily on social issues. Here, as in that fellow Rust Belt state narrowly won by Romney, the economy dominates voters' concerns, and Romney and Santorum both were playing to them.

And, as they could in Michigan, voters in Ohio will be able to declare party affiliation at the polls.

"We've got the same problems as everyone else does," said Gary Green, a 56-year-old Chillicothe business owner who attended a Santorum event Friday but still is leaning toward candidate Ron Paul. "We need jobs."

Sen. Rob Portman, a Romney supporter who plans to campaign with him at four events on Saturday, said Romney "doesn't have to win in Ohio, but it sure would help."

"I don't think people in Ohio thought this primary was going to be a big deal," Portman said. "They thought this thing would be wrapped up in Florida."

It isn't clear whether Santorum has any paid staff on the ground. As is the case elsewhere, Santorum is relying on volunteers and local leaders such as DeWine to power his campaign. Santorum's top aides still don't have a national campaign headquarters. Highway rest stops and advisers' hotel rooms are the base of their ragtag yet oddly durable operation.

His campaign faces another problem in Ohio. He failed to qualify for the ballot in three congressional districts, and party officials said Friday he filed an incomplete slate of delegates in another six districts, costing him up to nine delegates more. The state Republican Party would make the final determination on what to do with unallocated delegates based on party rules.

Santorum hosted his rally late Friday evening, hoping to generate the enthusiasm that helped him win the Iowa and Minnesota caucuses, as well as the Colorado primary and Missouri's nonbinding primary. He'll spend Saturday in the state as well, before traveling to Tennessee and Oklahoma. He's tentatively scheduled to return to the state Monday and stay through Super Tuesday.

Gingrich is short on cash and has been camped out in Georgia trying to prevent an embarrassing home state loss on Tuesday. But he's still a player of sorts in Ohio, where he plans one day of campaigning as well as a 30-minute, policy-thick cable television commercial about energy, an ad costing him $2,750 to run five times through Monday. The poll that found Romney and Santorum vying for the Ohio lead put Gingrich at 17 percent.

Paul, the favorite of the libertarian wing of his party, had 12 percent support in the poll. He planned no television ads or serious campaigning yet was sure to draw his fervent supporters to the polling stations for a campaign that has yet to win a state.

Gingrich planned to visit Ohio on Saturday to appear in a forum with former Arkansas Gov. Mike Huckabee and give remarks to a National Rifle Association event in Findlay and a GOP dinner in Bowling Green.

Campaigning in Savannah, Ga., Gingrich called Romney the "inside, establishment candidate" who would go to Washington "to manage the decay," and said Santorum would not change the status quo, either.

"We're not worried about losing Georgia," said Rick Tyler, a former Gingrich aide who is with a pro-Gingrich political committee that is spending almost $740,000 in advertising in Georgia. "But at the same time, he has to do well in Georgia." Tyler described the state as "a lot like South Carolina," where Gingrich pulled off his only victory to date.

In Bellevue, Wash., Romney implored supporters to come out for the Saturday caucuses, promising them "it won't take a long time, it'll just make a big difference." His Western campaigning included stops in North Dakota and Idaho. Massachusetts, Oklahoma and Tennessee are among the other Super Tuesday states.

Elliott reported from Washington. Associated Press writers Kasie Hunt in Bellevue, Wash., Ken Thomas in Savannah, Ga., and Julie Carr Smyth in Chillicothe, Ohio, contributed to this report.