If Clinton was elected President in 2016...

[The Right Honourable Martin Brian Mulroney PC CC GOQ]

Trump was obviously something of a phenomenon within the GOP, but he didn't even win a majority of votes during the primaries. He got about 45%, and considering the way primaries work (candidates drop out so vote percentages for remaining candidates go up over time), a clear majority of GOP voters didn't really want him (although they couldn't decide on who they did want, which is why the rest faltered). Had he lost to Hillary, the GOP establishment would have discarded his candidacy as an obvious mistake, even if some GOP voters remain personally loyal to him. You would think a majority of GOP voters would tend to agree with the establishment on this, because the majority, you know, didn't want him as the candidate. Losing to Hillary Clinton in particular would have been a particularly painful defeat to most Republicans, and Trump would be scapegoated for it.

In real life, what made Trump so powerful was that he beat Clinton, became president, and used the bully pulpit to punish dissenters in primaries. It became risky for Republican politicians to go against him, because clearly he had won over the majority of American conservatives, and wasn't afraid to cash that. In 2018, he became an asset to many Republicans who faced otherwise difficult challenges. Ted Cruz himself grovelled for Trump to keep his seat as a Senator. So even after he lost 2020, many dissenting Republicans were gone. In the Senate, there's Collins who represents a blue state, Romney who's a special case, and Murkowski an even more special case where the state party has disowned her and in 2022 she, a Republican, was in all but name the Democratic candidate in Alaska. That's the level of influence anti-Trump conservatives have right now. And in the current primaries, the two non-Trump candidates who are polling even in the teens, aren't anti-Trump so much as they're "Trump Plus". So for anti-Trump Republicans, save for those at the state level in some northeastern states, there is nothing to rally around, because he has the whole Republican establishment by the balls, and they can't do anything other than playing his game.

So back to a Trump loses scenario: this would not be the state of the Republican Party. Trump has had the upper hand in Republican political dynamics ever since his victory in 2016, but a defeat would turn things around. All those anti-Trump Republicans who lost relevance wouldn't have, and they would be in a position to use that relevance to crush his hopes for a 2020 run. Does Trump still run? Possibly, depending on how much popular support he has. He might even deny the 2016 election results, and convince a good chunk of voters, but not the Republican Party itself which would not have been as scared of him. But generally, having been the guy who lost to Hillary would have made a lot of Republicans question if they really wanted him to go for a rematch.