CHARLOTTE, N.C. – Republicans have no one who can match Bill Clinton's ability to deliver a forceful, point-by-point defense of President Barack Obama in the campaign's final two months. Luckily for Mitt Romney, Americans vote for candidates, not surrogates, and a coming cascade of Republican TV ads might drown Clinton's potent testimonial, which even GOP partisans call a masterpiece.

Obama could not have asked for a more detailed and emphatic rebuttal to every major charge leveled at him. Clinton will take his show to swing states in the next nine weeks, and Democrats will pray that newscasts and social media re-air countless snippets of his 48-minute convention speech.

Some commentators say the former president saved Obama's re-election. That's impossible to know, of course. Such predictions may look foolish if later events – say, disappointing monthly jobs reports issued Friday and in October and early November – boost Romney's call for a change in leadership.