Originally Posted by
atgilchrist
By and large the same way AB wound up with Stelmach. Anyone who sticks their head out too far, appears polarizing, or divides the party base will have a relative set level of support, but will be everyone else's third choice. The Dems have the added wrinkle of being simultaneously the New York Wall St party and the left wing option. Bernie and Bloomberg are in no way, shape or form politically similar, but were both fighting for the Democratic primary. The socialists can't stand the pro-business crowd, and vice versa.
Effectively, they eat their own, and the most inoffensive middle option takes the prize. It's how the parties have wound up with Biden, Jimmy Carter, Bobe Dole, Al Gore, John Kerry, John McCain, and many others.
Every once in a while, someone generates enough charismatic support to change things a bit - think Obama, Trump, JFK. Bernie has this charisma, but his policies are untenable to most thinking people.