Conventional wisdom says the base is 25-35%. But that number has a deep reserve that cannot be calculated. If the base turns out, it is because they all agree- and if they all agree they will be augmented by Libertarians, Christian Democrats, and Blue Dog Democrats. That is the magic that the Liberal Democrats cannot beat, that which leads to overwhelming success.
And what is “the base” willing to do to get to 51?
That is simplicity in itself. Give them someone to vote FOR.
I’m not sure you realize how alienated the libertarians and Blue Dogs are from the socons.