I have long argued that Democrats could have won in 1860 the same way they won in 1856 -- by remaining united in the face of split opposition parties.
In 1856 Pennsylvania's Doughface Democrat James Buchanan easily defeated the now split candidates of the old Whig party: Northern Republican Fremont and Southern American ("Know Nothing") Millard Fillmore, even though combined they received more popular votes.
In 1860 a united Democrat party would receive more popular votes than Republicans, but also benefit from a band-wagon effect to help it reach majorities in Border South & North states (i.e., Kentucky, Virginia, Illinois, Indiana)
But none of that happened because Deep South Fire Eaters engineered a split-up of Democrats making Southern Democrats now a minority within the minority Democrat opposition.
That's how Southern Democrats went from the cat bird's seat in 1856 to out of left field in 1860.
But I say: it didn't have to be that way.
It's possible, I guess. The only states that Lincoln carried with less than a majority were California and Oregon. Add their electoral votes to the states Lincoln lost and throw in the four electoral votes he got from New Jersey, a state he lost to Douglas, and it's still not enough to win.
To win, a Democrat would have to carry the whole South and the Border States and a big state -- New York, Pennsylvania, Ohio, or a combination of Indiana and Illinois. You could say that the party split hurt Democratic morale to the point where many Northerners who usually went Democrat voted for Lincoln or stayed home, giving their states to Lincoln.
But who Could the Democrats have run? Douglas was the strongest candidate in the North but he was hated in the Deep South. The other candidates were weak and unknown. Is it possible that a dark horse, an unknown Democrat could have kept the party united and defeated Lincoln, who was also a little-known figure at the time? It's possible, but a weak candidate might not have been able to unite the party.
There's another possibility. Horatio Seymour, the governor of New York, refused to run. If he had, maybe he could have carried New York and won the election. But he didn't. Maybe he's responsible for the Civil War happening when it did.
There's two wild cards, though. One is the Constitutional Union ticket, the old Whigs. Democratic unity wouldn't have kept them out of the race. They wouldn't have done as well as they did in a four party contest, but could still have taken a state or two from the Democrat.
The other wild card is the Southern fire eaters who already wanted secession. They would have found reasons not to support any Northern Democrat. A candidate that they would support would be unacceptable to many Northern Democrats.