What if Trump Drops Out

What if Trump Drops Out?

Although Trump is the official Republican nominee for president, he is displaying more and more cognitive and personal control issues.  Even his campaign staff and some of his high profile supporters are acknowledging this.

He almost certainly will not voluntarily drop out, but it is almost certain that he will continue to deteriorate mentally.

Can the RNC revoke his nomination?  Is there some mechanism to force him out, or are they irreversibly stuck with him?

If he somehow was removed from being the Republican candidate, how would a replacement be chosen and who might it be?

Would replacing him be good or bad for Harris winning the election?