The electoral college map flip; drift?

Over at Culture11 James Poulos refers to the Great Flip; the Republicans of 1860 were a regional party of the North and Greater North (e.g., California). Today to a great extent that is the position of the Democrats; the narrow wins by Barack Obama in Florida, Virginia and North Carolina were due to suffrage of non-whites (which wasn't an issue in 1860) and the "fake" parts of these states dominated by recent migrants from the North. Take a look at the map below to see the flip for yourself.

But the flip was not just regional, it was also ideological. In the wake of Abraham Lincoln's assassination there was a short period when radical was a term of praise in American politics as the scene was dominated by the Radical Republicans, and led by fiery and uncompromising men such as Thaddeus Stevens. Modern labels of "Left" and "Right" do not map perfectly onto the past, but I think that the term "radical" captures the cutting edge nature of the social thought of this faction of the Republican party. Thaddeus Stevens and Charles Sumner were a false dawn in American race relations, their outlooks were be such that little temporizing would be needed to justify their views in contemporary society.*

So what happened between then and now? You could point to specific well known historical events, such as William Jennings Bryan's rise in he Democratic party. Or, you could note that one reason Franklin Delano Roosevelt supposedly ran as a Democrat was that Theodore Roosvelt's sons were active Republicans in New York politics and FDR thought that there was more of an opportunity for a career in the party not already top-heavy in Roosevelts.** I suspect that the overall message here is that across decades political party labels are buffeted by stochastic forces, just as baby names are. Granted, currently the parties are shifted toward the Left and Right, which serves to constrain the random walk movement (there are positive feedback loops in terms of recruitment). But one never knows when an exogenous shock could scramble he alignment....

* The rationales were not the same, but it is ironic that the Republicans were the high tariff party while the Democrats were the party of free trade. Additionally, New England Republicans ironically fantasized about the emergence of a yeoman dominated South, resurrecting Thomas Jefferson's original vision.

** FDR's father was a Democrat as well, but note that for much of the 20th century party identity was a more fluid thing than today. Southern Democrats aligned with conservative Republicans, while liberal Republicans aligned with northern Democrats, more often than not. The reemergence of polarized regional politics in sharp focus is just a reversion to the 19th century pattern.