> Partisan polarization is a feature of the divide between the major parties in the two-party system aligning with the major ideological divides in the country,

> Partisan polarization is a feature of the divide between the major parties in the two-party system aligning with the major ideological divides in the country, which they tend to do in a normal stable political alignment, but not during a period of partisan realignment. A feature? I'm not aware of any document written by the American founders that calls this a "feature" of the system. An emergent property of FPTP perhaps but not a feature. I'd call it a mistake to attribute more to FPTP than its intuitive appeal; the American founders invented FPTP off-the-cuff. > The relatively low level of partisan divisiveness (despite the often quite high level of ideological divisiveness, seen in overlapping things like the Civil Rights Movement, the Anti-War Movement, the youth counterculture/“hippie” movement, etc.) in the (roughly) WWII to 1990s period isn't due to some kind of weird temporary absence of technology needed for partisan division, it is due to the long and overlapping partisan realignments spurred by (mainly) the New Deal Coalition and parties settling out their positions on civil rights. These things meant that on the politically salient ideological issues, the divide between the parties was not aligned with the major cleavages; “liberal Republicans” were farther left on the key ideological issues of the day than “conservative Democrats”, and the opposing ideological factions were present in both parties. Right but what _caused_ this political realignment? I mean sure, you can say that the ideologies were extant and during the Civil Rights Movement (and that this divide itself traces itself back to the Reconstruction period and before that into the founding of the US itself) the New Deal Coalition began unraveling and formed the seeds of today's divide, but I submit a large part of what exacerbated that divide was technology. FDR was a popular president and helped cement the New Deal coalition largely because of his use of radio. Likewise Goldwater and early televangelists received a lot of their support from the rise of TV. Social media is just the continuation of this ongoing technological trend.