The enthusiasm around Bernie is rabid. His supporters love him, are evangelical, and they fuging hate Trump and Republicans. That is an important set of distinctions. Nobody is that passionate about Joe Biden or Mayor Pete. Their greatest strengths are not being Trump, and if 2004 and 2016 taught us anything, just not being an unpopular Republican is not enough. If Sanders is the nominee the GOTV effort will be unprecedented and turnout will be high.
If Biden is the nominee we're getting four more years of Trump, I guarantee it.