If he does, understand that 1) POTUS left office with 95+% approval among republicans. 2) POTUS took a big chunk of black and hispanic votes. 3) POTUS has the backing of many dems / former dems, especially the blue collar types.
If POTUS starts a third party, it will NOT just "split the GOP"... there are plenty of voters who dems target that will be peeled away too. If they could be moved to vote fora republican, they can certainly be moved to vote for a non-GOP party.
Im leaving the republican party forever. FUCK THEM for what they did to Trump.