Journalistic accounts of the rise of polarization like the one in Thursday's New York Times almost always fail to provide two crucial pieces of context:
1. Partisan polarization has increased relative to the mid-20th century. But as I've pointed out many times, that period was a historic anomaly -- polarization is actually returning to the historical norm last seen in the late 19th/early 20th century:
2. The less polarized politics of the mid-20th century were driven almost entirely by the issue of race, which created a bloc of conservative Southern Democrats who acted as a virtual third party for much of this time. When Democrats are disaggregated by region (here in the House; Senate results are similar), the role of the Southern Democrats in depolarizing the parties becomes obvious:
In other words, the much-lamented era of bipartisanship in Congress was the direct result of a system of racial apartheid in the South. When it was removed, a reversion to a polarized two-party system was virtually inevitable. Unfortunately, almost no one involved in the debate over polarization understands these two crucial facts. It's incredibly frustrating.