MANCHESTER, N.H. — If this is Mitt Romney’s idea of a victory rally, one shudders to think what would have happened if he had lost the Iowa caucuses. The day after his impossibly thin eight-vote victory, the front-runner for the Republican presidential nomination flew here for a town hall meeting at Manchester Central High School, where he was to bask in the endorsement of his 2008 arch rival, John McCain. But the senator grimaced when he was introduced, and as Romney delivered his own stump speech, an increasingly impatient McCain pulled up his sleeve and checked his watch. McCain gave...