Sanders should withdraw his endorsement of Clinton and then seek the Green Party nomination for President. If he has any integrity after the WikiLeaks DNC dump, he would both withdraw his endorsement and get the Green Party Nomination for President (Sanders is not technically a member of the Democrats, so he doesn't have to leave the party - he just caucuses with them.
If they haven't had their convention yet, he would likely get the nomination if he seeks it. The Green Party leadership has more or less told him that. I can see him being a third party "Ross Perot" in reverse and end up costing the Clintons the White House as opposed as helping get them there. Sanders could end up getting 15% or more of the popular vote easily if he were to run as a Green Party Candidate.
Sanders can melt down the ‘Rat convention — especially if this scandal grows with more leaks in the next few days, he might even be able to pressure enough Superdelegates to switch their support to him. He makes it a “MAD” (mutually assured destruction) ultimatum for the 2016 race — either they nominate him, or he will devastate Shrillary’s prospects.
He can deny her the election, for sure. The Superdelegates may be persuaded that he is their only hope in 2016. I know it sounds far-fetched, but if he really thinks through his power in the current situation, he will realize that he can pull this off. Enough of his followers are so outraged that they would follow him to the Green Party, or stay home. The SuperDelegates will have to switch to him or else know they lose the presidency in 2016. Will Bernie have the balls to pull this off?
delegate counts:
Clinton 2205
Sanders 1846
SuperDelegates 650