I think the front runners are likely to torpedo each other and may be too polarizing (look at the last election). The DNC probably isn't going to push a candidate like they did last time (ie, this is how we got into this situation in the first place).

I think there is a danger of a strong candidate causing people to do what they did last time (ie, vote for the "opposite", Trump). The "left" politically is quite polarizing to the general culture and I do not think the people there realize it. Some of them things they think are "rights" are in fact extremely radical and important only to a very small minority.

Overall, I think Warren has the best chance at the moment. She is a she, not too radical about anything, and likely to appeal to the average person more than the others, and doesn't have the baggage that Biden might have.