I think they would only do so if he did something that was obvious to everyone to be a serious existential threat to the US's existence as a country.
I mean, it'd have to be something even more beyond the pale than ignoring the Constitution and transforming the US government into an authoritarian regime without the rule of law. Like, nuking China for no reason, or something.
Him: They’ll get as much as they want – tax cuts galore, deregulation, military buildup, slash all those poverty programs, and then get to work on Social Security and Medicare – and blame him. And he’s such a fool he’ll want to take credit for everything. Me: And then what? Him (laughing): They like Pence. Me: What do you mean? Him: Pence is their guy. They all think Trump is out of his mind. Him: So the moment Trump does something really dumb – steps over the line – violates the law in a big stupid clumsy way … and you know he will ... Me: They impeach him? Him: You bet. They pull the trigger.