Mott the Hoople
Sweet Jane
Yeah, the national party system really only started emerging in the 80's. Before then, there were often coalitions in different party that had a lot more in common with each other than they did with other coalitions within the same parties. Blacks did start turning to Democrats. I think this was primarily because of FDR. They were locked out of politics in the south anyway, and when they began to participate again in Mississippi, they actually chose to start a different branch of the Democratic party than join the Republicans. In Mississippi, I think the Republicans took advantage of this by primarily pursuing the interests of white voters, while the Democratic party attempted to moderate itself and, in the process, lost most of its voters to the Republicans, who's formerly somewhat progressive section was utterly devoured by the Dixiecrats fleeing to it. In the last election, 90% of white people in my state voted for McCain, and 99% of black people voted for Obama. I don't think this trend is as pronounced among white youth, though (Obama won the state among the youth demographic, something that wouldn't be possible without a large number of white voters).
The Republican party of Lincoln was really a different way different beast than the modern one. The Democrats were the states-rights party, and the Republicans were a federalist one (believe it or not, conservatives used to be highly federalist, something that repeated itself in the politics of many north and south American countries - the conservatives wanted a stronger national government, and the liberals wanted stronger state governments). The Republican's support of strong federal policy meshed well with black voters, who wanted strong federal power to balance their minority position in southern states. It also allowed them to integrate better into the more progressive segments of the party. When, under FDR, the Democrats began to use the federal governments power primarily help the poor and elderly, rather than to protect business and promote commerce, the conservatives turned against the federal government. They found that their views now meshed better with the states rights Democrats. The blacks, on the other hand, being largely poor, benefited largely from FDR's federalism, and became a solid Democratic constituency.
That's a very interesting analysis.