CHARLOTTE, N.C. (AP) — In a tight race for the White House, President Barack Obama exhorted college students not to forget him despite difficult times as Democrats shone the spotlight on his wife at the opening of their national convention.

Republicans weren't alone in pointing out the economic troubles in an election year shadowed by a sluggish recovery and unemployment of 8.3 percent. "It's tough out there" for many Americans, conceded Elizabeth Warren, running for a Senate seat now in Republican hands in Massachusetts.

Obama, campaigning at Norfolk State University, said things will only get worse if Republican Mitt Romney wins the White House this fall, and told his college-age audience that Election Day apathy was his enemy — and theirs.