Bernie Sanders appears to be the Democratic candidate who would be most vulnerable to Trumpian attacks that would result in defeat for the Democrats in November. He should not be the nominee for that reason alone.
Many of his supporters are so fervent that they risk dividing the Party to a fatal degree. Bernie has been almost Trumpian in encouraging their truculence. Many moderates who despise Trump might nevertheless sit the election out if Bernie is the Democratic nominee. It’s a worrisome situation.