Can a sitting President campaign for the person he wants to replace him? If so, I'd imagine the Democrats will use Obama to get out the black vote, similar to how they used Bill Clinton this year to energize the base in general.
Oh, of course Obama will be a schill for whomever the Dems put up next.
I'm just saying... all the black people driving around town with Barack Obama stickers on their cars? Yeah, they won't have Joe Biden (or whomever the Dems put up) stickers on their cars in three and a half years.
There will be a drop off in turnout.
But again, it probably won't matter. Exit polls once again show the majority of the young vote (18-29) voted Democrat, whereas the older vote was Republican. There's a changing of the guard. Republicans are going to have to make wholesale changes in order to re-appeal to the young, lazy, entitled folk out there who think the gubment owes them something.