Rick Santorum was making a meal out of Mitt Romney advisor Eric Fehrnstrom’s Etch A Sketch gaffe yesterday when the former senator got a little carried away. Honing in on the idea that Romney was a political chameleon who didn’t provide a clear alternative to President Obama, Santorum didn’t just stick to his usual line that nominating a moderate would guarantee a loss for the Republicans in November. Instead, he went one step farther:

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

Santorum may not have actually intended to say that re-electing Barack Obama is preferable to replacing him with Mitt Romney. But that’s the way it came out. And, for all of Romney’s well-known flaws, this sort of an overstatement illustrates one of Santorum’s: his penchant for going off message and saying things that will come back to haunt him. The candidate has always prided himself on being unscripted but along with the spontaneity comes a tendency to go on too long when answering a question. That often leads Santorum into uncharted territory. He doesn’t need a teleprompter. What he really needs is an internal editor.

This overstatement about Romney not being better than Obama isn’t going to cost him too many votes this weekend in Louisiana where he is heavily favored. But it is the reason why he has always found himself in unnecessary scrapes about tangential issues throughout his career. He may blame most of this on the press and there is some truth to this. But no journalist has ever put a gun to Santorum’s head and forced him to talk about contraception or pornography or to compare gay relationships to bestiality. Nor did anyone force him to write a book filled with such nuggets that were manna from heaven for Democratic opposition researchers during his landslide defeat for reelection to the Senate in 2006. He did it himself and usually without forethought merely because he chose to follow a question to its logical though impolitic conclusion.

In positioning himself as a bitter-end opponent of Romney, Santorum might think he can win some extra votes in the next few weeks as the primary campaign winds down to its inevitable conclusion. But if he doesn’t put a lid on such statements soon he will be doing himself some significant long-range damage. At some point this spring, Santorum will be forced to come to the conclusion that his presidential chances are lost and he will have to concede. That may be a bitter pill to him but if he wants to have a future in the Republican Party, he will need to do it. As I wrote earlier this week, Santorum’s remarkable primary run has re-established him as a national figure in the GOP. Should Romney lose this fall, he will immediately be seen as a major contender for 2016. But his chances in the future will be compromised if he spends the next few months sabotaging Romney.

Santorum has already walked back the comment and acknowledged that he will support the winner of the GOP nomination. But anyone who wonders why Santorum is falling short in this race and why he might not ever get to the top of the heap can look no further than his lack of verbal discipline. Unless and until Rick Santorum learns to watch what he says once he starts talking, he will never beat the Romneys of this world. For all of his passion and intelligence, the betting here is that he never will.