Republican leaders have a delicate task in how they treat the Birthers. They can't come too close without risking their credibility in the center, but they can't openly denounce them either, without alienating an important part of their base. The result in painful tap-dances like this from Eric Cantor:

MR. GREGORY:  There's been a lot of talk about discourse, about how you all can get along a little bit better and do it a little bit more civilly.  And I wonder, this is the leadership moment here, OK?  There are elements of this country who question the president's citizenship, who think that it--his birth certificate is inauthentic.  Will you call that what it is, which is crazy talk?
REP. CANTOR:  David, you know, I mean, a lot of that has been an, an issue sort of generated by not only the media, but others in the country.  Most Americans really are beyond that, and they want us to focus...
MR. GREGORY:  Right.  Is somebody brings that up just engaging in crazy talk?
REP. CANTOR:  Well, David, I, I don't think it's, it's nice to call anyone crazy, OK?
MR. GREGORY:  All right.  Is it a legitimate or an illegitimate issue?
REP. CANTOR:  And--so I don't think it's an issue that we need to address at all.  I think we need to focus on...
MR. GREGORY:  All right.  His citizenship should never be questioned, in your judgment.  Is that what you're saying?
REP. CANTOR:  It is, it is not an issue that even needs to be on the policy-making table right now whatsoever.
MR. GREGORY:  Right.  Because it's illegitimate?  I mean, why won't you just call it what it is?
REP. CANTOR:  I--because, again...
MR. GREGORY:  I mean, I feel like there's a lot of Republican leaders who don't want to go as far as to criticize those folks.
REP. CANTOR:  No.  I think the president's a citizen of the United States.
MR. GREGORY:  Period.
REP. CANTOR:  So what--yes.  Why, why is it that you want me to go and engage in name-calling?

Name calling! What a great term for openly denouncing a crazy idea.

He's definitely not a birther. But he doesn't want to be seen as anti-Birther. He just wants the issue to linger out there without touching it.