CHARLES KRAUTHAMMER: [Donald Trump] couldn't resist the temptation to be the smart ass and to show that he's clever. Look, the pride he has is his success. That's how he defines himself, and he wasn't ashamed to admit that he could have done this. He was actually conceding that he may not have paid any income tax. Now, in a boardroom with a bunch of other CEOs and you're boasting about your success, you say that. You don't say it in a presidential campaign.