A presidential reelection campaign needs three key elements: a defense of the incumbent’s record, a successful effort to define the opposition and a compelling vision of a second term.

President Obama may well celebrate a second term in Chicago next month, but the conventional wisdom underestimates the difficulty he faces, as his campaign has distinct problems with all three elements.

His defense of his record is exceptionally weak, his effort to define Mitt Romney is nearly exhausted, and his vision for the next four years — perhaps the most important — has been largely missing from his effort this year.