Yep. I think that's it. The E-Mails, while not innocent, in retrospect seem like huge neon lights AFTER you read the IM's leading Dems to be able to make the claim there may be a coverup and the Reps should have known. In a way, the E-Mails and the Reps responses to those E-mails validity smoothed the path for these "prank" IM's to be introduced into the conversation without any questions being raised as to their authenticity or their origin initially.
And this would explain the quick campaign commercial they had against Bachman alledging a coverup only a few days later.
The Reps at the Dems timing were made aware of the IM's, they ousted Foley probably sooner then the Dems thought they would though. The IM's grabbed the sensationalistic headlines and the Dems moved in for the kill by releasing the tamer E-mails the Reps HAD known about.
They they try to stoke the flames of the evangelical right to call for Hastert's resignation and alledge Republicans were trying to cover up for a homosexual that preyed on children.