I believe that it is premature to count the polls regarding the general election, especially before any debates. Once we have debates, then the point spread will be greater, separating the GOP contenders. By that time, I am pretty sure that Clinton's popularity will have fallen substantially. Biden's poll numbers are already competitive with Clinton's so we don't yet know where this is going. Hilary seems to assume she already has the nomination and won the election. Her arrogance may be her undoing. I don't even think Sanders is going to be a factor in the primary IF Biden throws his hat in.
I still think that any of the GOP candidates could beat Hillary if she gets the nomination. I really think that Biden would be harder to beat, as ridiculous as that sounds right now. Personally, out of all the possibles, if any Democrat has to win the general election I would rather it be Biden than Hillary or Bernie. At least Biden has a reputation from congress at working across the aisle. Democrat party leaders may very well get to the point where they feel that Hillary is a liability and dump her. It will be a hard decision because she is female and they really would like to exploit that angle. Hillary really has a lot of bailing to do to keep her ship afloat. Wonder why she is waiting so long. Maybe she knows that she doesn't have any answers to the questions that the media wants to ask. Or, she is hoping that she can keep the evidence of her criminal activity hidden.