I think there are other ways to deflect this attack.

Point out that the real problem these days with money in elections are the "527s", the independent, non-coordinated expenditures that groups like the Swiftboaters and others use to raise millions of $$$ to use in false attacks. Point out that there is already a Republican 527 that has announced it will spend $250mil to attack Democrats this year. And that is just one group.

Point out that the FEC, the cop that enforces the election rules, is out of commission at this moment because Bush has tried to stack that agency with Republican political operatives who would deny the vote to millions of the poor and minorities. And without a cop on the beat to enforce the laws, who would prevent McCain from breaking the rules?

Point out that his contributions come from millions of individuals as opposed to the corporate financing of Republicans who are then beholden to corporate lobbyists. That Obama is proud that the people, as opposed to the corporations, are supporting his campaign and that he would be robbing these people of their hopes and dreams if he prevented them from contributing. In fact, that is the real agenda behind this attack on the individual voter - McCain and the Republican Party would like to prevent as many people as possible from voting, especially if they are poor, a minority, or even just middle class working people. They think this country belongs to the rich, the powerful, and the corporations. And Obama will deny them that goal by continuing to allow individuals to contribute with their money as well as their support and good will. This time, in this election, I will not allow the Republicans to deny the people their voice.

Never defend, always attack. Turn the tables, put your opponent on defense. Muddle the question, bounce it back.