My son suggested the same idea(and he is not well informed on politics). I without thinking agreed but have had some time to think about it.
If the Dems went with left and lefter they would essentially limit their possible and probable voting groups to liberals only. So unless there is a huge Democratic Party turnout it sounds more like a recipe for failure than an opportunity to win the WH.
If they can find a centrist who can appeal to everyone to the right of Sec Clinton, they would be in a much better position to win. This is fairly standard general election politics and in this case it really makes sense.
