Republicans should have learned this long before now: Donald Trump doesn't care what you say.
You can strongly hint that he needs to tone it down. He'll amp it up.
You can say, "No woman should ever be described in these terms or talked about in this manner. Period." He'll shrug it off as "locker-room banter."
You can call his comments "the very definition of racism." He'll say them louder and tell his surrogates to back him up.
One argument for Republican establishment leaders to endorse Trump was that they'd be able to guide his campaign better from the inside — that he'd understand constructive criticism was intended to be constructive.
Instead, the reverse is happening. Republican establishment leaders aren't controlling Trump's message; he's controlling theirs, by providing an endless stream of controversies for them to respond to.
And even some of his fiercest critics (Ted Cruz, anyone?) have, under pressure, endorsed him.
It's easy to understand why Republicans who've endorsed Trump don't feel like they have any good options. See if you can do better.