Mentioning Trump, or any candidate, is just muddying the waters here. We’re dealing with a modern marketing machine that churns out a lot of vague ideas open to interpretation and a very few extremely specific ideas that on their own don’t really represent the adoption of any ideology wholesale.
In this way, candidates can be many things to many people, and the party can court from various strains of ideology and claim to represent a unified movement that doesn’t really exist. This is something any modern two-party state is probably going to have to deal with in the age of marketing and data science.
So really there are a few ways to approach the challenge:
Have the governance of the GOP be more strictly paleo.
Create a scenario where enough of the electorate is paleo that roughly 50% of our political infrastructure (in the form of a political party) is organized around them.
I guess guess a third option would be for the class of scenarios that get us a multi-party system with various parties more keyed to specific ideologies.
How to get a frequent plurality of voters to routinely vote the same slate is tough. Parties evolve and the paleo agenda...basically resists that. You’d at least need to butterfly the interventionism of WW2, or maybe better, have the situation in the immediate post-war world be read by most as a tremendous, earth-shattering mistake.
To get the pro- open markets, pro- cheap immigrant labor faction out of the GOP is also a tall order. The “reasonable men of business” had been their chief, even self-described stereotype since the 1860s.
I think it could possibly have been done in a 1950s conservative takeover. No one is more paleo than Taft. If he can get in power and fiddle with party bylaws in a sophisticated way and put the right people in charge, he could possibly morph the party in his image. I think several scenarios where disaster then happens for the GOP are the more likely outcomes than success, but it’s a system with no real margins. As much as I think change is possible, it’s certainly true that people can resist it with all their might, so perhaps the party system remains in place and the electorate’s just forced to adapt. Luckily marketing is on its way to make them think they’re being better represented.