Perhaps, but I think it is a big mistake to dismiss the financial angle in any effort to understand what is happening in any sort of political issue.
As I've said over and over -- and as historians have said -- they feared that Lincoln could use his appointment power to build up an anti-slavery Republican Party in the South.
I understand the concept of allowing unelected federal bureaucrats to "regulate" something they don't like to death, so this is not an idle fear, but again I think the financial end of this would have created pushback from the people making their wealth as a result of slavery (and I mean people in the North as well as the South) and it would not likely have materialized as anything significant.
Even in the maps you show, the elections of 1960, 1968, 1976, and 1988 do show some of the Great Lakes States voting differently from the Midatlantic Tristate area.
I noticed that, but those would appear to me to be special cases, and the map doesn't provide the details of how significantly they differed. It may have only been a few percentage points.
The same was true in 2016.
Trump made heavy inroads into the working class "rust belt" Union members, and that's why he won Michigan, etc.
Maps from the FDR era (say, 1928-1948) reveal a variety of different patterns.
I looked at those. FDR was a phenomena, and of course he was going to get reelected to a 3rd and 4th term. Did you look at the maps from 1900?
Going back further into the late 19th century, the South voted as a solid bloc, and the North voted almost as a bloc.
Yes they did and I suspect a lot of that was just keeping up the hatred for the other side. I think remnants of that pattern have been affecting elections perhaps even to the present day.
New York City's real electoral alliance was with the South. That started with Jefferson and Burr in 1800 and ended with Carter and McGovern in the 1970s.
New York was making a lot of money off of the South, but they were also making a lot of money from the industrialized great lakes states. (Midwest) They wanted both of those sources of money to keep flowing.
It's folly to think that Illinois or Wisconsin or Michigan were only singing New York City's tune in 1860. Such states were mostly agricultural then and no more beholden to New York
Look up the "Graingers."
But if you just want one big idea to explain everything, details don't matter.
There is a lot of noise in the data, but there is also what I see as a pretty strong "signal" if you understand how those references apply.
New York is a concentration of economic and political power and it always has been. It exerts outsized influence on the rest of the nation and especially on states that use it or rely on it for revenue.
So if New York votes to keep slavery, there is a fair chance that it will convince it's economic allies to do so as well.
You might like for every election to be each half the country voting solidly against the other, but elections where the two parties appealed to the same audience helped to hold the country together.
Did you look at the maps from 1900?
William Jennings Bryan was the voice of the Plains and a spokesman for the troubled farmers. He was also the first candidate (apart from Fremont in 1856) from a state west of the Mississippi. He had massive support from the West because of his silver policy (more in 1896 than in 1900). And massive opposition in the East and Great Lakes States because of they saw his silver policy as funny money. And of course, the South was solidly Democratic. 1896 (and 1900) weren't typical elections.
New York was making a lot of money off of the South, but they were also making a lot of money from the industrialized great lakes states. (Midwest) They wanted both of those sources of money to keep flowing.
New York was an industrial state and NYC was still an industrial city in those days. Policies that benefited Ohio or Michigan benefited New York. It might have been fashionable to think of NYC as a blood-sucking exploiter, but that wasn't the reality.
So if New York votes to keep slavery, there is a fair chance that it will convince it's economic allies to do so as well.
But it didn't. And the states that did ratify the amendment did so on their own, not at the behest of New York City or New York state.