Perhaps the diagnosis is wrong. What President Obama sees as "Democratic voter apathy" may actually be buyer's remorse. And as all American's don't fall neatly into Democrat or Republic boxes, assigning apathy to "Democrats" misses the point--it wasn't just Democrats that voted for him in 2008.
It's also wrong to assume his presidential legacy is the responsibility of "Democrats" to rescue and they're being apathetic on the up-take.
When Obamacrats voted for change they put "The Best of Obama" on their iPods and listened to them over and over, memorized the lyrics, and hummed the melodies in local government, facebook, and the pages of the NYTimes.
In many ways, they're feeling a lot like Republicans did after Bush passed NCLB and the huge prescription bill, and their malaise is for THE SAME reason. Republican melancholy was due to Bush's breaking a promise and Democratic lethargy is because Obama kept his promise.
But ultimately, both Republicans and Democrats were disappointed for the same reason. In essence, Bush acted liberal and Obama, well, is liberal.
The good news is, I still see a lot of Obama bumper stickers. The bad news I still see Mondale/Ferraro stickers. Maybe Obama's diagnosis isn't so far off the mark.