Sounds right, it’s just an all-or-nothing gambit or both you and the major party you align with would lose big.

You’ll have to appeal to the masses, get them willing to vote since voter turnout is not good, get awareness and enough energy to convince people to gamble on a vote for your third party since if each only get half of all voters on “their” side, the opposition wins. All while fighting the established party and all the funds, big names, etc. that empower it.

Heck, the US Democratic party has seemingly been willing to lose democracy than allow any progressive candidates to rise in the party.

first-past-the-post voting is the most common system in the States (and most prominent in presidential elections) which generally means additional parties rising to prominence will almost assuredly split the vote with the closest party so a new worker’s party will have to magically eclipse and obliterate the Democratic party overnight or they will both lose to the Republicans indefinitely.