My understanding of politics, such as it is, is that no political party is an individual and to be in the position of “top guy” he has to be voted there, by the members of his party and he only remains there, as long as he has their support.
If Trump does not secure the Presidency for another term, then he will have disgraced his party, to a certain extent, by believing in him and expecting him to be re-elected for the second term.
Failure of Trump to secure the Presidency again, will also be a failure of his political party to have achieved that too, bearing in mind that Trump fights dirty, is totally incorrigible and totally dishonest, cannot run the companies which he owns at a profit and has avoided paying income taxes for ever, owes the American Income Tax large sums of Tax he has so far avoided and has a huge amount of loans, plus interest to repay, soon, so that if he does not have the material assets to cover his expenses, he will become bankrupt.
Would any political party want Trump in charge, when he does not listen to advice, but does whatever Trump wants to do for Trump, to the exclusion of his political party, bearing in mind that before he was elected into the Presidency, last time, he was called “The Donald” and the only reason he won the Presidency was by undermining Hilary Clinton, when she was unable to recover, by casting doubt on her suitability to do the job.
If “The Donald” thinks he will remain in Politics, the above would be enough for his party to want to detach themselves from him and let him sink alone, as seems to be the case, if he does not win the Presidency again.
Trump might say he will continue in Politics, even if he is defeated, but with everything else, building up against him, I doubt if that is anything more than Trump bluster, much in the same way as a bully blusters, when events are about to overcome him and there is nothing he can do to avoid them.
Good riddance to bad rubbish, I say – one American President you should remove from the history books, like he never existed.