While I completely sympathize with the dilemma, the reasoning there is completely circular.
"I can't vote for him, because he cant win, because no one is gonna vote for him, because he can't win."
At some point we have to stop rewarding mediocrity. All the left has to do for us to capitulate and vote for a moderate/liberal Republican is to keep nominating a marxist. We will be so scared of the marxist that we will keep strategizing and playing by their rules. And voila, they get what they want.
No what it does is buy time. Getting a real Marxist elected is simply getting your nose cut to spite your face. The problem is that a lot of people think politics is over the day after election day and return to their sorry life and leave the field to the “activists” the result is you get professional politicians interested in themselves rather than serving their community.