There has not been a successful new party start up in the United States since the formation of the Republican Party in 1854, 162 years ago. And History is littered with the bones of many an effort. There have been Marxist parties, Socialist parties, populist parties, progressive parties, candidate-based parties, centrist parties, reform parties, revolutionary parties, even the present Green party. And that's just on the center-left side of the spectrum.
Some of those parties, like the Communist Party USA or the Socialist Workers Party are to be sustained presence, not by attracting voters in elections, but by creating a body of professional, or semi-professional, organizers united by a Leninist party structure. But no party, including them, has become an electoral power.
Yet, the dream of new electoral party remains the go-to dream of frustrated progressives whenever their candidate loses. As a threat to Democrats, it has a certain power, but as a sustainable organizational strategy, it is laughable. And its power as a threat is not that the new party might outpoll Democrats, but that it is an organized way to urge people to abstain from the election.
If you step back, it is not surprising that new party formations don't work. Instead of going to where the people are, it is going to where the people are not and waiting for them there.