It’s a turducken of hopelessness.

Turkey layer: Most of the United States has a first-past-the-post winner-take-all system of voting. There’s a great if old video by GCP Grey about this where he uses the animal kingdom as a somewhat cartoonish example. That if you start out with a cheetah, a tiger, an owl, a turtle, a gorilla and a chimpanzee all running for the office of King Of The Jungle, and all animals vote for their species, gorilla ends up elected with 19% of the vote. So 81% of the animals in the jungle now have a king they didn’t vote for. So the owl and the turtle drop out of the race, now you’ve got two cat parties and two ape parties, those who would prefer owl or turtle win have to either pick one of those to vote for or none at all. Then Cheetah voters get an idea: Yeah we’d like the Cheetah candidate to win, but Tiger is more likely to win than Cheetah, and we’d prefer Tiger to either of the two ape parties. So what if we vote for Tiger instead? The vote goes 40% to Tiger, 30% Gorilla, 30% Chimpanzee. More animals voted for apes but the tiger won because the apes split their votes across two candidates. This is called the Spoiler Effect, and you can see it in real life if you look at certain races in red states where a Democrat won pretty much entirely because a Libertarian ran and some people who would have otherwise voted Republican voted yellow instead of red.

Forming your own political party that is further to an extreme than one of the two major ones means handing more elections to the opposite side.

Duck layer: That assumes you’re allowed to create a party in the first place. Yes, the right to peacefully assemble enshrined in the first amendment of the constitution means that groups of people can hold meetings and say they’re the Leftist Party and whatnot, but the Republican and Democrat parties have inserted themselves into the workings of our government in much the same way a tick does. They have control over things like who gets to put candidates on ballots. “As duly elected person who decides these things, I decide to do things in the way that keeps me in power and you out of power.”

Chicken layer: A Leftist party is going to meet exactly once, the meeting will immediately devolve into a hair pulling match over identity politics and no platform will be built or second meeting scheduled. The American Left can do nothing but argue about whether it’s feminist or not to hate trans women or which ethnicity should the group feel most offended in behalf of?