Who would theoretically vote for the Republican Party from Fremont through Trump

[If my soul was made of stone]

Rich Midwestern German Lutherans.

[If my soul was made of stone]

What makes this hard is that Fremont was extremely socially liberal for his day.

Of course as one of the chief military strongmen of territorial California he played a large role in encouraging and even personally participating in the systemic genocide of the state's indigenous peoples. He was indeed very progressive on the key issues on which the 1856 election was fought, but still a product of his time in an unfortunate sense that gives a modern observer much cognitive dissonance.