In my opinion, the chances of beating Trump are:
Bloomberg 75%
Sanders 65%
Biden 50%
Buttigieg 40%
Warren 25%
Klobachar 15%
Steyer 10%
This doesn't reflect my preferences, it's just my assessment of whoever gets the nominations chances of winning. I think people have been sleeping on Bloomberg, he has money coming out of his ass, and if Biden can't comeback in the south and Buttigieg and Klobachar cant sustain their momentum the centrist in the Democratic party are going to need an anti-Bernie to keep the status quo intact, and since Bloomberg was a Republican until a year ago, he will have a lot of cross-party friends and allies in place.