Rick Santorum said this week that “of course” he would consider the vice presidential slot if Mitt Romney wins the Republican nomination.

“I’ll do whatever is necessary to help our country,” he said in an interview with the Christian Broadcasting Network.

{mosads}But there are a few reasons why it’s extremely unlikely he’ll ever have the chance to serve his country in that capacity.

First, it’s always a tall task to morph from being a candidate’s biggest opponent to his greatest defender, but that’s essentially what Santorum would be doing. 

And he would have to pivot from arguing that Romney is the worst possible Republican to nominate to explaining why the former Massachusetts governor is the most qualified person to lead the free world. That’s tricky. 

Politicians, of course, are notoriously adept at turning on politically convenient dimes, and it’s perfectly normal and expected for primary opponents to unite for the general election. But Santorum hasn’t been an ordinary primary opponent.

For over two years, he’s been railing against Romney for the Massachusetts healthcare plan, accumulating an impressive array of quotes Team Obama could use against Romney.

They all reached a crescendo in a February speech at the Mayo Clinic in which Santorum argued that Romney was “disqualified” from prosecuting the war on President Obama’s healthcare law. Romney has made repealing the president’s signature domestic policy initiative an important part of his campaign, but Santorum is on record as saying Romney’s disqualified from that argument.

Imagine a fall debate in which Obama could tell Romney, “Hey, everyone says your law is the same as my law — even your own vice presidential pick!”

But the former Pennsylvania senator has hurt his cause most dramatically in a series of statements over the past week that has left even his conservative defenders woozy. 

At a campaign event in San Antonio, he took his accusation that Romney is a “Massachusetts moderate” a bit further than usual, and essentially argued that there was no difference between Obama and Romney.

“If you’re going to be a little different, we might as well stay with what we have instead of taking a risk with what may be the Etch A Sketch candidate of the future.”

In other words: Obama and Romney are so similar that you might as well stick with the guy you already have: Obama. Immediately, critics pounced, and Santorum subsequently claimed that he was merely talking about what voters might think, not about what he personally thought.

But the damage had been done. Headlines across the country told the tale. CBS News splashed, “Santorum: If you like Romney, vote for Obama” across its pages, and conservative publications weren’t any kinder. Townhall magazine wrote, “Santorum suggests another Obama term better than Romney,” Hot Air ran “Santorum: Maybe America’s better off with Obama than taking a risk on an ‘Etch-a-Sketch’ candidate,” and Glenn Beck’s The Blaze wrote simply, “Santorum says Obama Superior to Romney.”

Santorum claimed that he was misinterpreted, but if so, he was misread by numerous publications sympathetic to his cause, including prominent conservative blogger Ed Morrissey, who had endorsed Santorum but threatened to caucus for Romney after hearing the quote.

Then, on Sunday, Santorum courted controversy again, calling Romney “the worst Republican in the country to put up against Barack Obama.”

Imagine what Team Obama could do with that characterization. Romney is already plagued with the perception of electoral weakness. How much worse if his vice presidential running mate called him “the worst Republican in the country” to lead the ticket?

University of Virginia professor and director of the school’s Center for Politics Larry Sabato claims that Santorum’s rhetoric has “eliminated any remaining chance” that he could be the nominee.

Yes, primary foes have turned into presidential tickets, but Sabato notes that Ronald Reagan and George H.W. Bush’s 1980 primary battle “never got bitter and personal,” and thus, their fall merger was much less messy.

“Politicians are famously adaptive, but a Romney-Santorum ticket would take too much adaptation,” he said.

Republican consultant Matt Mackowiak agrees, calling a Romney-Santorum ticket “implausible and virtually impossible,” thanks to Santorum’s recent rhetoric.

Vice presidential candidates are famously recruited to be attack dogs against the opposing party’s nominee, but Santorum would have just emerged from playing that role against the Republican Party’s nominee, and his believability would be considerably stretched.

There are a few other good reasons why Santorum is highly unlikely to be picked. 

The field of potential GOP vice presidential nominees is much too deep and talented — New Jersey Gov. Chris Christie, Florida Sen. Marco Rubio, Virginia Gov. Bob McDonnell, South Carolina Gov. Nikki Haley, Louisiana Gov. Bobby Jindal and Ohio Sen. Rob Portman all have strengths Santorum can’t match. And, to put it bluntly, they’ve all won their most recent races. Santorum lost his 2006 reelection campaign by nearly 20 points and doesn’t have nearly the fresh name or fresh experience that each of those prospects brings.

Another reason: Santorum has displayed a bit of a temper lately — arguing with a New York Times reporter about a question as video cameras recorded the exchange. 

In short, Santorum could become the headline in the fall, forcing the Romney team to spend valuable time and capital in repairing damage inflicted by its own vice presidential nominee.

Heinze, the founder of GOP12.com, is a member of staff at The Hill.  Find his column, GOP Presidential Primary, on thehill.com