Well, the entire field of Dem candidates are pretty much devoid of charisma (Sanders has a little, for stupid people anyway), and all the 'Of color' offerings were either visibly nonentities, obnoxious to normal people (Fartacus), or carrying a lot of whore baggage in the case of Harris.
Warren has the nails-on-a-blackboard screechy scolding thing perfected, and Klobuchar is an unlikeable basilisk.
It's not hard to see why Sanders is battling it out with a relatively-inoffensive gay dude for tallest midget.