McCain argues that flip-flops are an example of a political leader who can't be trusted -- so he might as well drop out of the race.

Democrat Barack Obama raised $52 million last month for his presidential campaign, more than twice as much as Republican rival John McCain in a significant boost to his financial cache for the fall contest.

Former President Clinton said Thursday he is eager to campaign for Barack Obama whenever the Democrat needs him, but has not given any thought to whether he wants to speak at the party convention in Denver.