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

[TransfemmeGoreVidal]

Probably a much bigger group then consistent Jackson through Biden Democrats tbh.

[Make America Grumpy Again]

At least 2/3rds of the current GOP and likely higher but more specifically:

Socially conservative rich people
Northern Evangelical Christians (With the small possibility of Bryan)
Southern Unionists
Nationalists (Although possibly not in 1880)
Imperialists
Fiscal Conservatives (Although some might've gone with Cleveland)
Wealthy suburbanites would've fit through 2012, although I imagine some held their nose in 2016 before going towards Biden

[I Will Not Be Wrong]

Northern businessmen, who have pretty much controlled the part since it's inception.

[Orser67]

Another common thread worth mentioning is opposition to immigration.

At least 2/3rds of the current GOP and likely higher but more specifically:

I agree with a lot of the groups you listed, but given how important the South is to today's Republican Party, I think 2/3 is a little high. Prior to the Civil War (and especially in 1856) Republicans had essentially no support in the South, and only minimal support in the border states. Those who would become Southern unionists mostly voted for Fillmore in 1856 and for Bell in 1860.

[darklordoftech]

Kansans, Nebraskans, and Dakotans.

[OSR stands with Israel]

Kansans, Nebraskans, and Dakotans.

they would have voted Dem in the 1930s though

[If my soul was made of stone]

Rich Midwestern German Lutherans.

[Skill and Chance]

Non-Southern, non-farm small business owners

What makes this hard is that Fremont was extremely socially liberal for his day.  For the same person to vote for Fremont and then not defect to Teddy Roosevelt, LBJ, Obama, or Biden requires a really strong attachment to Republican economics above all else. 

[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.

[Make America Grumpy Again]

Another common thread worth mentioning is opposition to immigration.

At least 2/3rds of the current GOP and likely higher but more specifically:

I agree with a lot of the groups you listed, but given how important the South is to today's Republican Party, I think 2/3 is a little high. Prior to the Civil War (and especially in 1856) Republicans had essentially no support in the South, and only minimal support in the border states. Those who would become Southern unionists mostly voted for Fillmore in 1856 and for Bell in 1860.

That is true, but demographics have changed dramatically since then. Had a rematch hypothetically taken place between then and now, I think there would be less differences than one would think.

[OSR stands with Israel]

Someone in Central PA though 1964 may be dicey here

[Skill and Chance]

Someone in Central PA though 1964 may be dicey here

1912 is also dicey in Unionist Appalachia because of Teddy.

[🐒Gods of Prosperity🔱🐲💸]

A few small regions that have been pretty consistently good for Republicans since 1856:

- northern Illinois, around Rockford to the south and east, and then on up north across the border to Walworth Co, WI.

- the area north and west of Columbus: the northeast Miami Valley + Delaware County.

- parts of southeast OH along the Ohio River (ex. Meigs Co.)

Dutch in Michigan have always been fairly strongly Republican going back to the beginning, though for whatever reason McClellan won Ottowa County in 1864, and in 1912 West Michigan preferred TR (himself a follower of the Dutch Reformed tradition).

[The world will shine with light in our nightmare]

Weren't several counties in eastern Tennessee/southern Kentucky consistently Republican from 1856/60 to 1960?

[🐒Gods of Prosperity🔱🐲💸]

Weren't several counties in eastern Tennessee/southern Kentucky consistently Republican from 1856/60 to 1960?

From 1864-present, but Fillmore in '56 and Bell in '60. 

[TransfemmeGoreVidal]

A few small regions that have been pretty consistently good for Republicans since 1856:

- northern Illinois, around Rockford to the south and east, and then on up north across the border to Walworth Co, WI.

- the area north and west of Columbus: the northeast Miami Valley + Delaware County.

- parts of southeast OH along the Ohio River (ex. Meigs Co.)

Dutch in Michigan have always been fairly strongly Republican going back to the beginning, though for whatever reason McClellan won Ottowa County in 1864, and in 1912 West Michigan preferred TR (himself a follower of the Dutch Reformed tradition).

I wonder if Ottowa County suffered a particularly high number of casualties during the civil war which led to a surge in anti-war sentiment.

[TDAS04]

Too bad Fremont wasn’t on the Missouri ballot; Gasconade County could have had the perfect record.

[Pericles]

Lots of people keep voting for a political party long after it is no longer the best fit for them, because they aren't that politically engaged and that's what they have always done. If someone gained immortality and lived from the 1830s to the present day, they might never break out of their early voting habits.

[Pacific Republican]

It would be difficult since the Republicans used to be liberal, and the Democrats used to be conservative.  But I guess if there are old conservative people in the South who still vote Democrat, then the opposite could exist.

[Secretary of State Liberal Hack]

It would be difficult since the Republicans used to be liberal, and the Democrats used to be conservative.  But I guess if there are old conservative people in the South who still vote Democrat, then the opposite could exist.

That is an extreme oversimplification of what were and remain pretty amorphous parties.

[Orser67]

Another region that has consistently been pro-Republican is the PA-NY border region known as the Twin tiers. Well, except for in 1912 and 1964, two elections that seem to account for a lot of broken streaks.