Well, it certainly wouldn't surprise me, at this point. As Bill Quick writes, "In the vein of LBJ and Walter Cronkite, I think it is fair to say that if George W. Bush has lost Peggy Noonan, then he has lost the Republican Party". (Though for a contrarian view, Ed Morrissey partially disagrees with Noonan's take.)
Glenn Reynolds has further thoughts on what he dubs the GOP's Death Wish--though, as I've said in the past, without the cool Herbie Hancock or Jimmy Page soundtrack to soften the blow.