One thing that he brought up was the fact that Obama gets these huge crowds to show up for his speeches, but those people aren't turning out at the voting booth.
(As an aside, the closest election since Super Tuesday was in Wisconsin, which Obama won by 17 points. If hs people aren't turning out, I hate to think how far behind Hilary would be....)
Apparently, Obama revognizes this, too. From Time (via DailyKos):
That level of energy was apparent at a Monday rally of several thousand people in Cincinnati. Obama opened his remarks by telling the crowd that early voting is already underway in Ohio and urged them to go vote immediately after the rally ended. He even told them the location where they could go cast their ballots. It was candidate-as-precinct-captain, and it showed both the intensity of the fight for votes going on daily as well as the benefits of having a candidate who used to be a community organizer and has run a voter registration drive.