Democrats have a turnout problem because they have a motivation problem. In 2010, their biggest problem was that they ran into an energized GOP electorate. The rise of the tea party movement and hostility toward Obama’s health-care law brought Republicans to the polls while Democrats stayed home. The president’s vaunted political operation seemed powerless in the face of that aroused opposition.

What Democrats learned in 2010 was that Obama’s personal appeal was not transferrable to Democrats running for the House or the Senate. Plouffe and others said at the time that it was essential for Democratic candidates to develop their own relationships with voters and not rely solely on the Obama organization to turn out voters. Some did; many did not.

A companion problem is confronting Democrats this year: dissatisfaction in their ranks. Obama has disappointed many of his followers, and his overall approval ratings are low enough to give the party real concern. The lack of enthusiasm for the president could easily lead to demoralization and too many stay-at-home voters in November.