In fact, most of the states Lincoln won in 1860 had often previously voted for Southern Democrat presidents, and often again voted for Democrats in years following the Civil War.
But 1860 was what we today call a "wave election", where the vast majority of Northerners suddenly awoke to the fact that the Southern dominated Federal Government was getting ready to impose slavery on western territories that didn't want it, and potentially even on their own states via the Supreme Court's Dred-Scott decision.
After the Civil War national voting patterns settled back to what they had been before: the Solid South allied with Northern big city immigrant voters.
This alliance won important elections in 1912, 1932, 1960 and led to today's welfare state as we know it.
The 1960s changed everything, especially 1964 when the Solid South first voted for a conservative, Mr. Conservative, Barry Goldwater, and Democrats took every other state, giving us President Johnson's "Great Society".
Today Dems have lost the conservative South, but they've gained even stronger holds on their traditional big city immigrant and other minority (especially blacks) voters.
Bottom line: in 1860 Lincoln's conservative party was based in rural and small town America, while Democrats were based on southern privilege-seekers and northern immigrants, just as they are, somewhat morphed, today.
Replacing the old Southern slave-holders we have today's huge "governing class" and liberal elites, but otherwise, pretty much the same idea.
Southern Democrats voted Democrat because they could never vote for the party of Lincoln. Simple as that. This changed in the 1960’s.
Fixed