@Paradise50 basically covered what I was gonna say, but yeah even with his status and abilities, Obama had a close run against the Clinton Machine. Its a testament to Obama's ability he was able to triumph over it, a lesser candidate (and lets be honest, Bernie is a lesser candidate than Obama) would have failed there. At this point, the Dems have to give Bernie the baton or else this stink will haunt them for generations.
IMO the best ticket to run is the Biden/Bernie ticket as Joe would carry the Obama voters for the most part and its an olive branch to the Bernie supporters because I truly think Bernie being the head of the ticket would bring up a lot of resentment among the remaining Clinton diehards in the party. That split, is the best overall course for the party, but because of that, you can expect the Dems to fukk it up...