Bernie is a nice man, but he's not electable. We need to pull in some Republican moderate votes, and they won't vote for a socialist. After the 2010 election and the gerrymandering done in the red states, it's going to get harder and harder to elect any Democrats at any level. Hillary is somewhat right of Bernie, and that makes her more likely to gather moderate Republican votes.
The Democrats MUST win this election and nominate a liberal jurist to the Supreme Court. We need a reversal of the decision on Citizens United. I'm sure Bernie would do that, and he seems like a very nice guy. If I thought he was electable, I might vote for him. I just don't believe he can be elected.
BTW, I'm new here. I'm age 74 and a moderate Democrat in California. Whoever wins, let's hope it's a Democrat. Down with the Koch brothers!