Barack Obama said Friday, “We’ve had a rough couple of weeks.” Actually, he’s had a rough couple of months. He’s lost three big primaries to Hillary Clinton. And, should he hold on to win the nomination, he can no longer be considered a clear favorite over John McCain in the general election. In a New York Times/CBS News poll in late February, Obama was defeating John McCain 50 to 38. Two months later, the Times/CBS poll had McCain and Obama tied. The poll that came out yesterday showed Obama reopening a lead over McCain — but clearly over this period...