I give my wife constant grief for reading the Enquirer, but she never fails to point out that there have been many times when they have accurately broken salacious "news" like this, John Edwards being only the most recent example. Bigfoot and aliens can't sue for defamation, but celebs and politicos can and do. The Enquirer has top notch lawyers that know this.
Call me a convert; I believe this. That said, it should mean no more than it did with Bill Clinton. I suspect, however, that there will end up being a "double"-double standard here, since Palin is not only a woman, but a family-values conservative Republican.