Trump will lose.
If he loses by a small margin, little will change within the Party. Trump himself - an obvious addict of attention - might even run and win again in 2020. And lose again.
If you want to hasten the reform of the Republican Party into something that offers sane and viable candidates, you should do all you can to make sure that Trump's loss is decisive. If you want to continue to lose presidential elections until at least 2024, possibly later, then make the 2016 election close.