Third parties cannot work in our system, as stand-alone organizations.
Because of our winner-take-all and Electoral College system to have power, the “third” party has to become popular enough to become one of the two major political parties — either by displacing it or replacing it.
If it displaces one of the old major political parties, that old party then either goes away or labors in Loserville as a minor party.
If it replaces one of the old major political parties, it either keeps the old name (say, Republicans) but in fact is a new/renewed party or it gets a new name (say, TEA Party).
So, I agree with you.