If he only wins Vermont and/or New Hampshire, he will be reasonable and suspend his campaign around April-May. If he does this, it will be interesting where his supporters go, especially since I don't believe Bernie will endorse Hillary. Hillary cannot win without Bernie's base, and I suspect a large number of us will defect to third parties, or even a decent Republican candidate like John Kasich, if only to send a message to the DNC that it is unacceptable for them to keep fielding us corporatist Democrats.
He's endorsed every Democratic candidate since who, Mondale? And I'm pretty sure Clinton has always been the general Bernie voter's second choice in the polls, even with Biden, the three stooges, and other/no one as options.