Media Matters notes that, in his August 12 broadcast, Limbaugh floated the notion that maybe John Edwards got jiggy with Rielle because:
We know -- we've been told that Elizabeth Edwards is smarter than John Edwards. That's part of the puff pieces on them that we've seen. Ergo, if Elizabeth Edwards is smarter than John Edwards, is it likely that she thinks she knows better than he does what his speeches ought to contain and what kind of things he ought to be doing strategy-wise in the campaign? If she is smarter than he is, could it have been her decision to keep going with the campaign? In other words, could it be that she doesn't shut up? Now, that's as far as I'm going to go....
It just seems to me that Edwards might be attracted to a woman whose mouth did something other than talk." Limbaugh went on to say in a subsequent segment: "my theory that I just explained to you about why -- you know, what could have John Edwards' motivations been to have the affair with Rielle Hunter, given his wife is smarter than he is and probably nagging him a lot about doing this, and he found somebody that did something with her mouth other than talk.
I don't know that this tells us anything useful about the Edwards' relationships. But it certainly sheds some light on why Rush is thrice divorced.