Former Pennsylvania senator Rick Santorum greets supporters at a rally at Dayton Christian School in Miamisburg, Ohio, on Monday. (JIM YOUNG/REUTERS)

Poll after poll shows the Buckeye State’s GOP primary in a dead heat.

But to hear former senator Rick Santorum (R-Pa.) tell it, his campaign is the David to former Massachusetts governor Mitt Romney’s Goliath.

In an address to nearly 400 enthusiastic supporters at a packed American Legion hall here on primary eve, Santorum blasted Romney for having outspent him “12-to-1” in Ohio.

And after weeks of being sidetracked by discussion of contraception, education and other issues, Santorum returned to his criticism of Romney’s conservative record, contending that his GOP rival is a political opportunist who shifts course depending on what’s “fashionable” at the time.

“Governor Romney has spent $12 million in the past month in the state of Ohio,” Santorum told the crowd, to an audible “Wow” from the audience.

That amount, he continued, is more than Gov. John Kasich (R) spent during the entire course of his 2010 election bid.

Santorum — who has been investing heavily in Ohio himself but who has also been out-organized by Romney — cast Romney’s TV ads as overly negative and portrayed himself as “somebody who will lift the country up.”

And in a rare conference call with reporters ahead of the event, Santorum excoriated Romney on the matter of trust.

“The underlying problem that I hear when I talk to people all over — they say they just don’t trust Mitt Romney to not do what’s the fashionable thing at the moment,” Santorum said, arguing that his GOP rival has shifted with the political winds on issues ranging from global warming to the individual mandate.

On health care, Santorum made the claim that Romney — because of his overhaul of Massachusetts’ health-care system while governor, which included an individual mandate to purchase insurance — would not be able to take on President Obama on the matter.

“Why would we put someone up who is uniquely unqualified to take him on on this issue? You don’t think it will be used against him? ... It will be a drumbeat. We will take an issue where we’re on the offensive and turn it into a liability. I don’t care how much money he has — don’t let that happen, Ohio.”

Santorum defended his emphasis on social issues in the campaign, although he did so only briefly.

“If we’re just the party of lower tax cuts, we’ll never win another election,” he said.

“Sen. Santorum's base is Obama supporters,” said Romney spokeswoman Andrea Saul, in an e-mailed response. “The last thing the White House wants is to have to face Mitt Romney in a general election, so Sen. Santorum is relying on them to throw the primary in his direction.  Mitt Romney has won five contests in a row and won in every corner of the United States with Republican voters.  It’s going to take a businessman who is not a creature of Washington to change the status quo.”

Santorum did not reserve his fire solely for Romney, however. He also devoted a considerable portion of his Westerville remarks to slamming Obama on foreign policy, energy and the economy.

The president, he said, has “a two-letter energy policy: N-O.”

Obama also erred in apologizing for the burning of a pile of Korans at Bagram air base in Afghanistan, Santorum said.

“I will not apologize for our troops in the Middle East,” Santorum said to applause. “This is the tactic of the radical Islamists: intimidation. Get you to back off.”

And Santorum called on Obama to “man up” and not to blame his predecessor, George W. Bush, for the country’s economic woes.

“I will never mention the former president by name while I’m in office,” Santorum pledged — unless, he added, he was referring “nicely” to him.

This post has been updated since it was first published.