You're right -- we may not. Best historical example we have is Nixon, and Watergate.
After Nixon, the GOP brand was at its lowest point ever. But what happened after voters punished us at the polls in '74 (especially) and '76? We had a huge GOP tidal wave in 1980 because we had a different candidate/candidates. I actually think the GOP leadership and various candidates have done enough to separate themselves from Trump overall (heck, even Hillary has said that Trump is an anomaly in the GOP) that our next round of candidates will get judged on their own merits, not Trump's.
At least, I think that scenario is more likely than is Hillary not putting a vise-grip on national office for Democrats. That's really the point for me -- that recovering from Trump is more likely than recovering from Hillary.
I think we can likely recover from a Trump defeat. Like you said, even Hillary would admit he's an anomaly in the GOP, and a clear repudiation of Trumpism at the polls will grease the skids for the alt-right to be purged just as they should have been in the first place (and would have been, back in my day).
I'm not saying I'd elect him in order to impeach him. I'm saying that if he crosses lines that shouldn't be crossed once election, then we can/should/will impeach him.
He will have less institutional support in the other branches of government -- and in the military -- than any President in history. The Democrats absolutely despise him and would likely vote for impeachment day one if they thought they could win. More elected Republicans in Congress have affirmatively distanced themselves from Trump than from any candidate, ever. You don't think Paul Ryan would support a vote for impeachment if Trump did something unconstitutional or criminal? He'd call for that vote in a heartbeat -- much rather work with Pence. Same If he were to win, then sure, he'd be impeachable, but at that point he will represent the GOP and conservative brands. It's only by defeating him that the brands' reputation can be restored.
with McConnell, and Pelosi/Schumer would happily board that train. Trump would be toast.
How do you think he'd resist that? Congress would vote to impeach him, the courts wouldn't back him - they're all filled with traditional GOP and Democratic appointees who also would have no particular love for Trump. So what's his play when given the boot? Call out the Marines? I can assure you, they wouldn't play that game either.
If he were to win the election, then sure, he'd be impeachable, but at that point he will represent the GOP and conservative brands. Maybe such impeachment would be easy, maybe it would be hard, but at that point we'll have a monster on our hands put in office by the vote of a majority of voters. Again - don't underestimate the tenacity of a man given that kind of power.
It's only by defeating him in this election that our brands' reputation can be restored. For most of this election season I was focused on nominating a candidate that could defeat Clinton. In my opinion (and I understand and respect that you disagree) Trump's worse because Trump is existentially far more dangerous, especially to our national security because he's so damn crazy. So my goal at this point is defeating Trump. I think that's the better result for the nation, although it may really be just a choice of which orifice to be screwed in. But I think the repudiation of Trumpism is absolutely necessary to save conservatism. And not a close defeat either - a landslide, humiliating defeat is what is needed to cleanse the stables.
One thing I'll concede before a single vote is counted - if Trump is defeated I'll have no ill will towards those Republicans who've made the difficult choice that you will. I've always been of the view that solidarity is a good thing, and realize I'm breaking with that value for the first time in forty years. In a lesser-of-two evils election, reasonable minds can differ as to who is the worse evil. I say it's Trump, you say it's Clinton. I'm voting my conscience in the face of a Hobson's choice, and so are you. That's all one can reasonably expect of any citizen - take one's duty seriously and make a decision that lets you sleep at night.
After this is all over, I hope the clans can reconcile. I hope to be able to do my part to accomplish that.