He's laying the groundwork to opt-out of the public finance system in the general election. This is so important, because swamping McCain could lead to a result where the needle isn't just moved slightly in one direction but instead is turned to 11. It would be a sledgehammer to the Berlin wall of conservatism.
I do find it highly amusing the mock umbrage the cons are taking to this. Change your mind on campaign finance and you're apparently a confidence man, but lie the nation into a doomed conflict and they want to put you up on Mount Rushmore.