Pandering to the Fringe
When it comes to actually pulling the lever--or hanging a chad--for the Democrats, fewer and fewer are willing to make the commitment. Sure, they would like a better choice, a choice that forces Republicans to be "smaller government" conservatives and/or offers the citizenry more social liberty, but that is not the choice. The choice is between "no idea" Democrats and treadmill Republicans.
Perhaps if Democrats cannot pull off even taking the house they will have a discussion about who they are and what they are not. History shows they should make some major gains, but at best the gains may be marginal. At some point they have to acknowledge they have little to say that the citizenry wants to hear. Perhaps they will realize they are pandering to a vocal fringe.