As we head into the presidential campaign's final days, both candidates are laboring under a burden. Obama has failed to articulate a crisp rationale for his second term; he has not answered the question of why the next four years would be better than the last  under his leadership.

Romney's problem is different. He is doing a good job of finally focusing on the economy, to the exclusion of other issues, and beginning to convince people that perhaps he is a man with a plan. But he is in danger of having his both his tax plan and his jobs plan exposed as frauds.

These  doubts — Obama's blurry vision and Romney's lack of credibility-- are the final hurdles for both as they approach the campaign finish line. Who will jump cleanly?