As you know, Rick Perry doubled down on his birther flirtation this morning, claiming in an interview that Obama’s birthplace is “a good issue to keep alive.”

“It’s fun to poke him a little bit and say `Hey, let’s see your grades and your birth certificate,’” Perry added.

I thought it would be worth asking the campaigns of the two frontrunners — Herman Cain and Mitt Romney — for comment on this. Are they willing to condemn it? After all, Romney has vouched for Obama’s U.S. citizenship in the past and has made Perry’s unelectability central to his campaign, and it seems likely that Perry’s flirtation with birtherism will fuel doubts about whether he has the gravity and temperament to be a good general election candidate.

No luck.

Both campaigns declined to address Perry’s comments. “We’ll pass,” Cain spokesman J.D. Gordon emailed. A Romney campaign spokesperson also declined comment.

This comes as some Republicans are raising questions about Perry’s birther flirtation. Jennifer Rubin reports that two GOP governors — Terry Branstad of the all important state of Iowa, and Bob McDonnell of Virginia — are now condemning the comments. As Rubin put it: “the message is unmistakable: Knock it off. You’re hurting the party.”

Karl Rove also condemned Perry’s dalliance with birtherism, which he called “nutty.” Rove said: “It starts to marginalize you in the minds of some of the people whom you need in order to get the election”.

But — for now — the two leading GOP presidential campaigns are not willing to go here. Could it be that they worry that condemning Perry’s remarks risks alienating conservative GOP primary voters? Cain, for one, has said the burden is on Obama to prove he was born in the United States. Romney, however, has stated flatly that he thinks Obama’s “citizenship test has been passed.”

In many ways the birther issue is a proxy for generalized Obama hatred: Donald Trump enjoyed short-lived popularity with GOP voters in part because his birther circus act demonstrated a general willingness to attack Obama in as visceral a way possible. Perry seems to be calculating that he can benefit in this way, too. If and when Romney is asked to respond to Perry’s latest, it’ll be interesting to see if he’s willing to condemn Perry’s birther dalliance, or whether he worries whether doing that will raise doubts about his anti-Obama bona fides.