Trump going third party is the scorched earth/burn it down option, it won't magically accomplish anything else. It's a Butch Cassidy and Sundance moment, go down swinging if you're going down anyway
If there were a viable fourth party with equivalent draw on the left, that might throw open the door to break the unipartry - but either new party could win it
I don't see either wing of the uniparty suddenly getting religion on doing the people's business just because they survive a third party scare
Trump runs 3rd party, RFK runs 4th party.
Would absolutely devastate the uniparty beyond any repair.
There'd need to be some gentleman's agreement to make this happen successfully though, with both advocating for each other to get some new viable parties in the running. I think they'd also need more time to make this happen, than the time we have left.
I could see it happen, it's less far fetched than the "2 more weeks" nonsense everyone was clinging to for years.
Make it a campaign issue.