Herman Cain is the flavor of the month in Republican presidential politics.

But if the arc of the 2012 presidential race tells us anything, it’s that social conservatives — and conservatives more generally — will tire of the former Godfather’s Pizza CEO at some point and once again search for the next big thing.

“It’s become the whack-a-mole primary,” Republican strategist Mark McKinnon said. “Whoever sticks up their head gets hammered.” He added that “GOP primary voters sense Obama is vulnerable and they are desperate for a gladiator to take him on, so candidates get elevated to extraordinary heights so quickly they can’t maintain the altitude.”

Jan van Lohuizen, a Republican consultant who handled polling for President George W. Bush, suggested that the volatility is the result of the relative anonymity of the field. “This is the first time we’ve had a primary where most conservative candidates are unknown,” he said. “We don’t have an ‘old familiar’ with good credentials running, and that has not happened in a while.”

Cain is the latest of a type that began, amazingly enough, with reality television star Donald Trump, who surged in opinion polls before deciding not to run.

Then came Rep. Michele Bachmann (Minn.) whose 15 minutes of fame appeared to end on Aug. 13, the day she won the Ames Straw Poll and the day Texas Gov. Rick Perry entered the race.

Perry’s rise among conservatives was meteoric but his fall has been equally so. His position on immigration as well as his executive order mandating that teenage girls receive the HPV vaccine have raised questions about his conservative bona fides. (Of this group, however, there’s little question that Perry is the most likely to be the nominee because of, in large part, his fundraising ability.)

Enter Cain, who has zoomed to the top tier off the strength of his rhetorical gifts — he gave the best speech, without question, at Ames — and a surprising victory in a Florida straw poll last month.

Amid the Cain hype, however, there’s reason to doubt his staying power. The candidate has struggled to retain top staff members — in key early-voting states such as Iowa and nationally — and, as a result, has only the barest traces of a political organization to capi­tal­ize on his moment. (His campaign says it’s increasing staffing but shows few signs hiring.)

Cain also has been somewhat gaffe-prone, having to apologize for insisting that he would not want a Muslim in his Cabinet and arguing, oddly, that although he has a team of economic advisers, he wasn’t willing to divulge their names.

“Cain is the early fall fling,” said one Republican operative who is monitoring the race. “But few really expect Cain to get the nomination, least of all Herman.”

If Cain isn’t able to sustain his momentum, who might fill the void? The two most obvious candidates are former House speaker Newt Gingrich (Ga.) and former senator Rick Santorum (Pa.).

Gingrich has already bottomed out in the campaign — his entire political team quit earlier this year — and reenergized his effort with several solid debate performances. Santorum is the tortoise of the field, watching while more charismatic figures such as Bachmann and Cain eclipse him and hoping his moment comes.

Of the two, Santorum seems the more likely option. He finished a solid third at the Values Voter Summit over the weekend — a sign of a spark of momentum? — and has a campaign team on the ground in Iowa. Add to that the fact that he is a down-the-line social conservative with a voting record during more than a decade in Congress to back it up and it’s possible that Santorum is the next best choice to fill the lingering void among conservatives.

“I think Santorum is the next flavor,” predicted one senior Republican strategist not aligned with any of the candidates. “But if Cain can prove he has some endurance, he may become a flavor that hangs around a while.”