Ohio's place on a pedestal is simple: No Republican ever won the presidency without victory in Ohio.
Romney claimed a 3 percentage-point primary victory in his home state of Michigan and a 20-point margin in Arizona.
Among the 10 Super Tuesday states, Ohio is considered the bellwether prize. Candidates and their third-party organizations -- aka super-PACs -- spent a collective $5 million on television ads a week before the primary.
A University of Cincinnati poll released last week showed Santorum ahead by 11 percentage points, but a Quinnipiac University survey had him up by 7 points.
The University of Cincinnati poll also indicated 16 percent of Ohio Republicans were behind former House Speaker Newt Gingrich and 11 percent backed U.S. Rep. Ron Paul of Texas, who hasn't claimed victory yet this cycle.
The stakes are highest for Gingrich, who campaigned in several Super Tuesday states at the expense of last week's primaries in Michigan and Arizona.
Gingrich has said a win in Georgia, which he represented in the House, is "central to the future of our campaign," but his campaign told CNN it hopes also to capture delegates in Ohio, Tennessee, Oklahoma and parts of Idaho.
In the weeks leading up to the Michigan and Arizona primaries, Romney and Santorum each claimed to be more to the right than the other on social issues, which has political insiders concerned because the fiery rhetoric may be good to land conservative votes in the primary, but likely will turn off the crucial independent vote needed in November, The Washington Post reported.
"We need to move on to having a nominee, so we can speak with one voice out there and begin drawing that contrast with [President] Obama," said Ed Goeas, a Republican pollster who worked for Rep. Michele Bachmann of Minnesota, a former presidential contender.
Another question for Romney is whether his anti-automaker bailout sentiment will affect him negatively in Ohio, which, like Michigan, relies heavily on the auto industry. Romney supported Ohio Gov. John Kasich, a Republican, in his effort to restrict public unions' collective-bargaining rights -- a move overwhelmingly rejected last fall by voters in this union-heavy state.
"The number one thing is the auto bailout," Eric Kearney, a Democrat from Cincinnati and minority leader in the Ohio Senate, told the Post. "Ohio is the second-largest auto producer in this country. We rely on that. It's a substantial portion of our economy. The first thing Mitt Romney says, and he repeats it, is he is against the auto bailout. Those are Ohio jobs he's talking about that he doesn't want to retain. I don't get what his strategy is."
And there still is the problem of ill-timed statements Romney's made throughout the campaign. Romney acknowledged on Tuesday that his gaffes have not been helpful to his cause. Republicans in Ohio agreed.
"People are like, 'Yeah, he's probably going to win, but I really don't like him, and I'm not going to vote for him,'" a top Ohio Republican who requested anonymity to speak freely with the Post. "That's the collective zeitgeist."
Add it up and "Romney is suffering from the same soft feelings among Republicans in Ohio as he is everywhere else," a high-ranking GOP official in Ohio who's not backing any candidate in the race told CNN. "And don't forget, a big swath of this state is basically right next to western Pennsylvania, where Santorum's wheelhouse was."
Santorum doesn't get a pass, though. He has built a collection of statements and positions that also threaten his appeal to moderates. He has embraced culturally conservative positions, including opposing abortion and criticizing the government for curtailing religious freedom, which goes against the views of a majority of voters in nearly every national poll.
After his narrow loss to Romney in Michigan, Santorum has been playing up his hardscrabble western Pennsylvania upbringing when stumping in small, working-class towns, such as Steubenville and Georgetown, across Ohio, which just happen to border Pennsylvania.
Romney "must take the battle to Santorum in the most important Super Tuesday state, Ohio," University of Virginia political scientist Larry Sabato wrote in his blog last week.
One thing on Santorum's side of the ledger is that Ohio has a higher percentage of evangelical voters than Michigan, the Christian Science Monitor reported. The Ohio Poll showed Santorum with a 45 percent-to-20 percent lead over Romney.
Sixty-six delegates, which are apportioned based on the vote, are at stake in Ohio.
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