For Mitt Romney, running against President Barack Obama is like trying to beat himself.

Although he pulled out a narrow Super Tuesday win in the critical swing state of Ohio, Romney still couldn’t beat back primary challenger Rick Santorum and he’s fighting off what MSNBC analyst Howard Fineman called the “fundamental queasiness” of the Republican electorate that handed him wins in Alaska, Idaho, Massachusetts, Virginia and Vermont but also gave Santorum wins in North Dakota, Oklahoma and Tennessee.

One reason the door’s still open for Santorum is that there was egg on Romney’s face this week after BuzzFeed’s Andrew Kaczynski unearthed a 2009 USA Today op-ed in which Romney said Obama should “dump the public option” and “help the poor buy private insurance” — which is, of course, what Obama ultimately did.

Romney’s healthcare plan isn’t exactly breaking news, but his op-ed reminded GOP voters once again that Romneycare begat Obamacare.

If he winds up as the nominee, it’ll be hard enough for Romney to take on Obama with health care, but that’s not the only issue he should worry about. On most of the big debates of the Obama era, there’s been a point in time — however brief — when Romney’s held pretty much the same position as Obama.

The two are really pretty similar.

Obama and Romney are both millionaire Harvard lawyers — tall and trim, cool and calm — with immaculate salt-and-pepper hair and picture-perfect families. They’re both minorities — one ethnic, one religious — and neither one of them served in the military.

Sure, they disagree on abortion — but Romney was pro-choice before he wasn’t.

And Romney says that only he can stop Iran from getting a nuclear bomb — but it’s tough for anyone these days to out-hawk Obama — the guy who took down Osama bin Laden and Muammar Gadhafi in the same year.

Romney says he’d repeal Dodd-Frank — Obama’s banking-sector regulations — and if he gets elected, he would probably try to roll back Obamacare. That’s something that the Republican base would almost certainly demand. But if you rewind the Obama era, it’s harder than you think to find issues on which Romney would have gone a different way:

In a 2010 interview, Romney confirmed his support for TARP when he told Fox News’ Neil Cavuto that saving the banks “was the right thing to do” since it was “an investment made to try and keep a collapse of our entire financial system from occurring.”

In a 2009 interview, Romney expressed support for the stimulus, telling CNN’s Wolf Blitzer that “I think there is a need for economic stimulus. Americans have lost about $11 trillion in net worth” and “government can help make that up in a very difficult time.”

In a 2009 USA Today op-ed, Romney touted the same payroll tax cut, small businesses tax credit and Bush tax cut extension that Obama has enacted in the last couple of years.

In his widely-read 2008 New York Times op-ed, titled “Let Detroit Go Bankrupt,” Romney called for failing U.S. automakers to undergo structured bankruptcies, like those that Obama imposed, before loaning GM the money it recently used to regain its place as the world’s number-one seller of automobiles. The difference between their plans wasn’t the loans, but Obama’s insistence on bailing out the United Auto Workers’ pensions, too.

Which brings us back to health care reform.

USA Today wasn’t the only place that Romney touted his plan. Although it’s no longer available on their website, Romney made the same case in a 2006 op-ed for the Wall Street Journal — arguing that one of the features of Romneycare was that in it, “we insist that everyone purchase health insurance from one of our private insurance companies.”

In other words, Romney didn’t just support the individual mandate — he bragged about it.

The irony for Romney and his supporters is that he’s been selling himself — and is widely seen as — the only candidate who can beat Obama. But, in fact, he’s the GOP candidate who’s most like Obama. Before he unseats the president, Romney ought to explain why he agreed with him so many times in the past.

Swerdlick contributes to WNYC’s “It’s a Free Country” blog. Follow him on Twitter at @swerdlick