CHICAGO — President Obama and challenger Mitt Romney spent the last few days frantically barnstorming swing states for every last undecided voter, but the election’s outcome will hinge more centrally on crucial turning points over the course of a multiyear campaign.

These are the victories and defeats and calculated statements of the last many months, the uncontrollable events and debate blunders and gaffes caught on video. They add up to a portrait of the contenders for the White House that has shaped their public image, for better and for worse.