So it's now pretty clear that McCain has violated campaign finance laws, to the point that even CNN has noticed (-ish*). To quote the Boston Globe (via AMERICAblog):

The senator from Arizona has spent $58.4 million on his Republican primary effort. Those who have committed to public financing can spend no more than $54 million on their primary bid.

McCain's lawyers contend that the spending cap no longer applies. The senator was certified to enter the matching-funds program last year when he was starved for cash. But once he started to win, he decided to hold off. On Feb. 6, after his Super Tuesday victories, he wrote to the Federal Election Commission to announce he would withdraw. His lawyers said that gave him freedom to spend as much as he wanted.

But David Mason, chairman of the commission, wrote to McCain's campaign last month to alert him that the commission had not yet granted that withdrawal request, and that the commission would first have to vote on the matter.

I'm a bit too cynical to believe any of this'll actually end up hurting McCain, but by all rights it should be devastating (he wrote the law!). At Firedoglake, you can sign onto a complaint, to be delivered to the FEC on Monday. They're just a few hundred signatures short of their goal of 30,000.

[A good summary of the original loan is here; a note about the FEC complaint filed a month ago by the DNC is here.]

* - Maybe they reported it more extensively elsewhere, but I wouldn't want to give them too much credit based on the clip I just linked to, since that clip wasn't so much "look what McCain has done" as "look what those wacky liberals are saying McCain has done."