At the risk of being a conspiracy monger, I would like to suggest an alternative explanation to recent events.
Perhaps Corsi is not really interested in a run at the US senate, per se. Perhaps it is a ploy.
Kerry has threatened to sue Corsi for slander. If that were to go to court, it would require full disclosure. (Slander is only provable if the accusations can be proven false). Therefore, such a trial would require that Kerry sign his SF-180. (This issue has already been widely discussed in FR).
However, Kerry is in a tough spot: if he wants to make a run for the 2008 presidency (a chimerical notion IMHO), he would have to sue to remove the threat of the SBVT. Therefore, most have concluded he will not sue.
But, maybe Corsi is forcing Kerry's hand. If Corsi could mount a credible attack on Kerry's SENATE seat, then Kerry might be compelled to respond with a legal suit. Or, perhaps Kerry's supporters would force Kerry to do so (believing, in their delusion, that Kerry would win such a suit). Then, Kerry would be forced to sign the SF-180 as part of the disclosure process.
Kerry finds himself in the classic Catch-22 conundrum. And, Corsi may force him there. Don't sign and don't sue, and remain vulnerable not only against a presidential run but for retaining his beloved Senate seat. Sue, therefore sign, and release all of his records. Tough spot.
If Corsi were to pull this off, it would really be sweet, and an extraordinary accomplishment.