That's what Barack Obama has done:
"Barack Obama opted out of the federal public financing system Thursday, setting himself up for a huge cash advantage over John McCain in the general election — but also providing his critics with a large opportunity to criticize his claim that he is committed to change in Washington."
Seems like a rather significant about-face, given that last year he pledged to use only public monies for the fall campaign, as long as his opponent pledged to do the same. Well, his opponent made the pledge. But now, Obama won't go along.
Doesn't seem much like "change we can believe in" to me.
That having been said, this also shows why all the hoo-hah in favor of campaign finance reform etc is just that--hoo hah. Even those ostensibly in favor of it, such as Obama, will abandon it at the first opportunity. We don't need limits on spending. Just make every donation made to every national candidate instantly transparent and a matter of public record, and then let the voters decide if they're bothered by them.