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.
Look at the coal industry in this era. We owe the rise of labor Unions in a large part to New York controlling the value of coal and setting the price low enough to cause massive labor unrest.
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.
Seward guaranteed that New York would pass it, and I think he knew what he was talking about.
On another website, I have another civil war discussion going on, and a point was made about what would have happened had the South capitulated quickly after the invasion.
I put forth the point that it was likely an absolute certainty that the Corwin amendment would have been ratified in an effort to avoid a future conflict.
I think if the South had given up quickly, we would have a constitutional amendment protecting slavery forever.