Why in the world did he go blabbing about it? What did he possibly think he had to gain?
…if only because his essay* rather conspicuously danced around even trying to work out a rationale – which is odd, because said rationale is really fairly simple. In reverse order: what Joe Sestak thought that he had to gain was the Democratic nomination for Pennsylvania Senate. He was the underdog against the establishment candidate (and turncoat) Arlen Specter: the White House was on the other side; and Sestak was using an anti-establishment gambit. So he became the Guy Who Wouldn’t Be Bought.
As to why Sestak’s still blabbing about it: well, now that he’s won the nomination – and, incidentally, been bought – I’m sure he doesn’t want to be. But there’s the pesky problem that he did use this incident to campaign – something that few (if any) of the supposed counter-examples offered by Establishment Democratic flunkies did themselves – and it does happen to be illegal, and the official explanation is fairly slapdash, and gets more so with every new iteration. And as the above links show, this was as much an issue to the GOP back in February (when Specter was still the favorite) as it is in May, and will be in June, July, August, September, October, and the first few days of November…
…after which, it will of course become merely a footnote to Pat Toomey’s election.
*Executive summary: Joe Sestak is a Bad Man for bringing up something that is no big deal and everybody does, even if it is technically illegal and stuff, and the White House is simultaneously not at fault, perfect, and messing things up.