He'll probably lose by a similar margin as Hillary Clinton. The most electable candidate would be Sanders, because although he has that socialist label attached to him, he's pretty effective in pivoting to broad issues that have majority support, or at least sound reasonable. In addition, he's able to take Trump to task on things like trade, which Clinton and Biden failed and will fail to do in a General Election. It will be close, but I think if Bernie is the nominee, he'll win. Biden won't excite enough voters and his record is way too easy to attack. The worst thing for Sanders is his 1980s Soviet stuff, which was so long ago and had no effect on how he governed. Anyways, just my hot take, lol.