Third party candidates and parties exist. They don’t suddenly cease to exist simply because the 2 right-wing parties we’ve had forced upon us have gone out of their way to prevent them from participating.
Ah yes, the great and amazing third parties of the US. In this corner we've got the Libertarians, aka the "republicans that like weed and dislike age of consent laws" party, and in the other corner we have the Green Party, aka the "pops up every election year to complain how both sides are bad, before promptly returning to the ether upon the elections conclusion" party.
Such good options, I truly don't know why anyone wouldn't want to vote for one of those two. /s