That’s not how it works. You want to force the party left then build movement from the ground up. Go out on the corner and collect signatures to change your voting system to ranked choice instead first past the post. Run for local office as a socialist or green.
The fact that all you have to do is once every 4 years push a button should tell you that it’s not the right thing to do to effect change.
Presidential elections are not about voting for a perfect candidate, very few elections are ever about that. They are about putting someone in power you are most capable of negotiating with. The person that is both capable of winning and closest to your ideals.
It does actually work that way, at least sometimes. If a major party loses enough votes to a third party, it forces them to adjust their platform at least enough to win back would-be voters.
Whenever third party voters honestly tell people that they are voting third party because it closely aligns with their values, and that neither major party is even slightly compatible, major party apologists and cheerleaders come out of the woodwork to saying actually you’re one-of-us, you just don’t know it yet, and if you just vote hard enough for my candidate then things will get better. It’s been over a hundred years of least dirty of two shirts, and it’s not getting better.
Every four years it’s “the most important election of our lives”, and if we’re not scared into voting D it’ll be the death of Democracy itself. Sorry, I’m not a buyer. My state had a double-digit R majority in 2020, it’s not in my interest to vote for a candidate I don’t want.
