You'd think midterms would be a great time to get your name out there and run high profile candidates to win House districts led by charlatans...
The "get your name out there" idea is the problem.
For a third party to be successful they'd need to first build a massive grassroots movement behind it. That takes a lot of effort and may not be successful.
And what happens if you build that grassroots movement but the Democrats say "hey people seem to care a lot about this issue so lets put it on the platform." Then what if the Dems actually deal with that issue? Well then that grassroots movement was a success! Except the leaders of the movement may not "get their name out there" as their name isn't on a ballot that everyone sees.
Basically US third parties are mostly about giving name recognition to a few individuals (who may or may not have brain worms) so they can get on TV and have some notoriety. People voting third party feel like they're sticking it to someone... when really the people they're sticking it to don't have enough votes to do much and the people they're voting for just want to be on TV.