Rick Santorum has made much of Mitt Romney’s deviations from conservative orthodoxy. He’s shown little sympathy for the argument that those from blue states sometimes must bend and collaborate with Democrats if they hope to get anything done.

But Jonathan Martin nails it when he finds that Santorum was the ultimate home-stater, often taking decidedly unconservative positions in representing a state much less liberal than Massachusetts:

For a Pennsylvania Republican, and especially a social conservative like Santorum, constituent service, bringing home federal checks and trumpeting his clout was a necessity for political survival. It was part of his appeal to members of both parties back home. But that half of his political personality — Rick the Rust Belt pol — left a trail of controversial votes and odd coalitions that are proving hard to explain to conservatives.

“I always thought that there was Rick Santorum in Pennsylvania and a Rick Santorum in Washington,” said longtime Philadelphia Democrat Larry Ceisler, noting the duality of a politician who could be doing battle on the Senate floor with Barbara Boxer over partial-birth abortion on a Thursday and strategize with the Building Trades unions about how to score federal money for the Philadelphia Housing Authority on a Friday.

By the way, I don’t think it is unrealistic to expect senators from Maine or Pennsylvania to have different voting records than those from Texas or Utah. But since Santorum made an issue of political purity, he should be judged by the standard he set for his main opponent.

Martin details some of Santorum’s detours:

In his 2000 reelection, when he launched “Democrats for Santorum,” the senator touted his ability to work with the popular mayor of the state’s largest city. And six years later, fighting for his political life, Santorum aired a spot that sounds jarringly different from his current persona.

“The right thing to call me is passionate about helping the families of Pennsylvania,” Santorum said in the ad, noting that he had been called both too conservative and, by backing an increase in the minimum wage and opposing Amtrak cuts, too liberal. . . .

It wasn’t just projects where Santorum built relationships with [organized]labor: he also opposed efforts to expand right-to-work laws and supported Davis-Bacon, the prevailing wage law for construction workers.

By 2006, the perception of Santorum as a social conservative crusader among many rank-and-file voters, combined with a toxic environment for Republicans, proved fatal to his Senate career.

None of this is that extraordinary, nor does it detract from his overall record as a conservative. But, as with so many things, Santorum’s excessive rhetoric does him a disservice. Rather than painting himself as the only “real conservative” and excoriating Romney from also making accommodations to liberals in his state, he would have been better off and more honest portraying himself as a pragmatic conservative who was able to get a lot done for his state and make conservative advances.

He now has to explain, midstream, why his record (with votes for earmarks, Big Labor concessions, Medicare Part D, No Child Left Behind, opposition to free trade and with his support for Arlen Specter’s presidential bid) make him all that more conservative than Romney on domestic economic issues.

He certainly is to Romney’s right on social issues and he is equally hawkish when it comes to national security, but on the critical economic issues, it’s not all that clear he’s any more consistent or any more conservative than Romney. Santorum has made his fiscal record look even worse with a harebrained scheme for special tax treatment for manufacturing.

Santorum is now in the unenviable position of appearing too extreme on social issues and insufficiently conservative on fiscal issues. Had Romney been more expansive about his own tax plans and offered an earlier, more detailed portrait of his gubernatorial record, Santorum might have encountered difficulty earlier in the campaign. But Santorum now has trouble in large doses, with a debate tonight and a short time to meet the high expectations he set for himself in Michigan.

Simply being the best of the enormously flawed not-Romney’s (e.g. more stable than Newt Gingrich, more articulate than Texas Gov. Rick Perry, more knowledgable than Herman Cain) is not enough to win the nomination; he’s going to have to prove himself to be what he advertised — the most conservative, electable Republican. Right now there’s considerable doubt about both the “most conservative” and “electable” parts of that equation.