If Trump loses the GOP will disintegrate.
Any rump party remaining will simply be an appendage to the Congressional Democrats.
JD Vance, Tulsi Gabbard, RDS and maybe RFK jr will have to get something new off the ground. The GOP has no central organizing principle which can command a national majority now or in the forseeable future.
The reality is we do not have a “nation” to organize any more—so in a post Trump world (win or lose) the parties are little more than appendages of wealthy and powerful special interests.
Both parties have the same issues.