public funding.

I have a questions about public funding for candidates' campaigning. I know McCain and Obama both originally decided to use public funding for their campaigns, but Obama withdrew that once he was fundraising much more than the $89 million set aside for him. But now that he is financing on his own, what happens to the $89 million? we were talking about this in one of my other classes, and we all didnt know where it goes. Back to the government to use? Or set aside for a later campaign, I'm unsure. I would like to say it would go back to the fed. government to use for something good, but I dont know. Maybe you would have an answer or idea?