If you want to get an actual left winger into office in the us you have exactly three options, entryism into the democrat party and pushing a left winger in the primaries (ie bernie, maybe AOC in the future), building up a new party starting by taking local offices in progressive places until the dems either have to pivot to the left or are replaced by you, revolution.
Ignoring reality and voting for a third party in the presidential election is nothing more than posturing at best and actively enabling the worst elements in society at worst.
So why dont you just vote for yourself? Clearly thats the only way to agree with your candidate 100% and it clearly doesnt matter to you what the odds of winning are.