I’m pretty sure that Trump, as a share of population size at the time, got a higher % of primary votes than Reagan did.
Nope. Reagan 59.8% Trump 44.9%.
Reagan ran against 2 others, GHWB & John (a bad joke) Anderson.
Trump against 16? 17? That discrepancy would impact the difference in percentages towards Trump closing that gap and support the contention of the subject.
Nobody made any headway but Reagan and Bush (and Anderson), so the others exited early on.
That was one of many signs that the party was more united behind Reagan in 1980 than it is behind Trump now.
The bottom line is that a majority of primary voters cast their ballot for Reagan in 1980.
No candidate got a majority in the primaries this time (there may be some caucus votes in the totals, but I don't think that changes the overall picture).
I'm not putting Donald Trump down. I'm just suggesting we tone down the exaggerated claims and flawed comparisons.