…I can see it kinda, but a lot of Goldwater’s success, both in winning the nomination and reorienting the Republican Party was that his supporters captured local party institutions, in world where primary elections were somewhat advisory and nonbinding and party officials had more control over candidate selection (this changed between 1968 and 1972).

Trump’s running in a world where those changes have shaken out and power is held less in the hands of formal party officials and more in the hands of movement activists and the media, and it’s hard to predict what kind of legacy the Trump campaign (be it successful or not at any given stage) will leave - Obama for America was kind of a substitute for a party-based infrastructure and after Obama’s success was absorbed into the official Democratic apparatus, on the other hand on the Republican party independent power bases (most notably the Kochs’ Americans for Prosperity) have been making moves to supplant the party structure entirely.

One thing to keep an eye on is how a Trump victory (as GOP) would change the balance of power between executive and legislative wings of the Republican party.

For most of the 20th century political scientists bemoaned the lack of “responsible party government” - ideologically coherent parties such that voting for the “conservative” party would necessarily produce more “conservative” results. For example under the New Deal system that essentially survived in Congress until the 1994 “Republican Revolution”, an urban northerner voting for a liberal Democrat could actually increase the chances of conservative policies, as a congressional majority would put conservative southern Democrats with seniority in charge of the powerful committee chairmanships. Ditto for conservative western Republicans strengthening the hand of northeastern liberal/moderates.

Like I said, 1994 changed a lot of that, completing an alignment along ideological lines for the legislature at least (and giving parties more control over chairmanship assignments in the ensuing reforms). Since then Republicans have relied more on their legislative power - routinizing supermajority requirements in the Senate, conducting the second impeachment in American history and grumbling in favor of a third, with budgetary shutdowns and showdowns essentially trying to bootstrap a Vote of No Confidence into existence.

A Trump win though, or even a nomination that establishes the ability of an independent actor, in alliance with (something that passes for, if possibly in style more than substance) movement conservatism to control the Republicans’ executive apparatus, against the will of formal party figures… honestly I have no goddamn clue how that’d play out, but like I say it’s worth keeping an eye on.