It’s a trap.
I used to think that, but now I am not so sure. While a 3rd party might not win a presidential election anytime soon, it is quite possible for one to win some congressional seats, and there is plenty of precedent for that. If a 3rd party were to win a significant number of House seats, perhaps as few as five or ten, for example, it would control the balance of power, with its influence extending far beyond its numbers.
Every County GOP party in my neck of the woods is an ardent Trump supporter. I don’t see them supporting a third party. It will only diminish them.