One thing I just noticed...the Democratic vote percentages in the last three presidential elections were within less than a point of each other (49.23%, 48.38%, 48.27%). Last time that happened you ask? 1880-1888. Last time it was true of the Republicans? Also 1880-1888. If stability is an element of polarization, and I think it is, then yeah, these are merely the most polarized times since the Populists first arrived.
And if we extend the analogy to expect history's repeat ....
The Dems win 2008 with less than 50% due to a significant 3rd party vote. Then, the GOP wins a decisive string of presidencies, defining the national direction for a generaion.