ARE YOU crazy about Barack Obama? Do you fervently hope the next president of the United States will be as similar to the current president as possible? Then Donald Trump may be the candidate for you. Of all the candidates running for president, the one who most resembles the incumbent is not Hillary Clinton or Bernie Sanders or Martin O'Malley. To be sure, the Democrats' policy views largely overlap with Obama's. But when it comes to attitude and self-image, it's Obama and Trump who are birds of a feather. Everyone knows about Donald Trump's bottomless narcissism; this is a man...