Interesting -- John McCain apparently thinks that pointing out that his opponent is a Birther, or caters to Birthers, will help him win a Republican primary:

I haven't seen any other Republicans attacking their colleagues in competitive races for being in bed with the Birthers. I certainly hope this works. In an environment of mass unemployment and Democratic flailing on the Hill, Republicans are going to gain a lot of seats regardless of what they advocate. There needs to be some check on the party's descent into madness.