I don’t think the Republicans have the cojones to do this, but they could stop Trump.
Just change the rules on the first day of the convention to say that nominees must have served 2 years in a public office.
This is assuming that a majority of the delegates are not Trump people, even though they may be pledged to vote for Trump on the first ballot.
Of course, chaos would result. But the Republican party would not have to give their funds to Trump and would live on to fight another day.
But, given the lack of leadership anywhere on the Republican side, I don’t expect anything like this to occur.