LOUISVILLE, Ky. - Can people trust what Barack Obama says?

Republican presidential candidate John McCain said on Saturday that, at least in some instances, they shouldn't.

Campaign finance was the issue at hand. McCain, speaking at a Republican fundraiser that netted some $2 million, slammed the Illinois senator and presumptive Democratic nominee for going back on a promise to take public funds during the general election if his Republican counterpart did the same.

"This election is about trust and trusting people's word," McCain said. "Unfortunately, apparently on several items, Senator Obama's word cannot be trusted."

Harsh stuff. Obama, who broke fundraising records during his victorious primary fight against New York Sen. Hillary Clinton, said he made the decision to forego public funds because the Republicans had become masters at gaming the "broken" public finance system.

Sticking to his original promise would have limited Obama to spending $84 million in the two months between the Democratic convention and the Nov. 4 election and barred him from taking additional donations.

McCain does not expect to match Obama's fundraising success.

A spokesman for Obama said the Republican candidate had a history of his own when it came to changing stances. "Senator McCain's path to the nomination required repeatedly changing his positions to appeal to the Republican base," Tommy Vietor said.

"From supporting Bush tax breaks for the rich that he once voted against, to saying he'd now vote against his own immigration reform legislation, the John McCain of 2008 is completely different from the man we knew just a few years ago."