He didn't do anything to cause Hillary to lose, I'm not saying you are saying that but she hurt herself and it's annoying AF when I hear people in the media blame Bernie bro's or Sanders supporters for her loss, she wasn't owed their votes it was up to her to earn them. Most of them likely wouldn't have voted in the first place, he was getting people interested that otherwise would have just sat home.
I don't blame him and he campaigned hard for her but when he no longer had a path to win he should have no longer have been attacking her. He could have kept talking his issues to push her to the left but attacking her when he had nothing to gain just cements people's negative views on her. He even has important people on his campaign that voted third party in swing states and we can't have the run back on that thinking again. The election is too important.
He can't be stubborn this time around. I don't care if its Joe Biden and he drops dead after he wins the nomination. Drag his corpse into the White House like its Weekend at Bernie's.