One hears frequently about the Tea Party extremists who are binding the hands of Republican moderates (I know, I know), but a pull away from center is hardly a GOP phenomenon:

Bell’s defection is one of dozens by state and local Democratic officials in the Deep South in recent months that underscore Republicans’ continued consolidation of power in the region — a process that started with presidential politics but increasingly affects government down to the level of dogcatcher.
“I think the midterms showed you really can’t be a conservative and be a member of the Democratic Party,” Bell said.

The much-lamented polarization goes both ways, and one interpretation is that the American people are just not satisfied with the slow drift toward a bureaucratic superstate facilitated by parties of only mildly different flavor.
Another interpretation is that people are trying to pull a leftward-drifting political class back toward the center-right. Either way, the disruption of the old order is not necessarily an unhealthy development. Perhaps we’ll wind up with real political competitions rather than elections that merely adjust the speed at which insiders tug the polity in their preferred direction.