Is polarization really at a historic high? I'll pull the latest research comparing today's divide to past eras.
In the United States, the answer depends on timeframe and measure, but by most modern quantitative measures polarization is worse than it has been in the past 50-150 years, though not necessarily worse than the Civil War era:
Yes - by recent historical standards it is at or near record highs
•A Pew Research Center analysis finds that, on average, Democrats and Republicans are farther apart ideologically today than at any time in the past 50 years. The analysis notes the current standoff is the result of trends playing out for decades.
•Polarization among U.S. legislators has increased since the 1970s, with rapid increases in polarization during the 2000s onwards. Following a period of a much more balanced Congress during the middle of the 20th century, ideological distance began to grow during the 1970s to the extent that Congress is now more polarized than at any time since the late 1870s Reconstruction Era.
•Using DW-NOMINATE scores, researchers note partisan elites in the U.S. are as polarized today as they were around the time of the Civil War.
•There are now only about two dozen moderate Democrats and Republicans left on Capitol Hill, versus more than 160 in 1971-72.
•Since 2002, when Republican Rep. Constance Morella was defeated and GOP Rep. Benjamin Gilman retired, there's been no overlap at all between the least liberal Democrats and the least conservative Republicans in the House. In the Senate, the end of overlap came in 2004.
•Across 10 political values Pew has tracked since 1994, there is now an average 36-percentage-point gap between Republicans and Democratic leaners. In 1994, it was only 15 points. Across 48 different questions, the average difference now stands at 18 percentage points…nearly twice the size of the gap in surveys conducted from 1987-2002.
•Members of both parties who have unfavorable opinions of the opposing party doubled between 1994 and 2014.
•Affective polarization (dislike and distrust of out-groups) has seen a substantial increase over time in levels of affective polarization in the United States, unparalleled in other democracies. One measure shows between 1992 and 2016, mean out-party feeling has declined from approximately 50 out of 100 (or “neutral”) to roughly 25. A multi-country comparison found that in the U.S., affective polarization has increased more dramatically since the late 1970s than in the eight other countries they examined — the U.K., Canada, Australia, New Zealand, Germany, Switzerland, Norway and Sweden.
•Some observers summarize this as “Partisan polarization is worse today than it has been in 100 years,” and the 1950s and 1960s, by contrast, were marked by high levels of political bipartisanship.
Nuance - not necessarily worse than the most divisive periods, and elite vs. mass distinction matters
•Historians note The Gilded Age of the late 19th century (c. 1870 – 1900) is considered to be one of the most politically polarized periods in American history, with open political violence. Some scholars argue today's levels are "not such an alarming anomaly compared to those occurring during the time of slavery".
•One history expert argues “The most divisive time in our history was in the years leading up to the Civil War,” — “it’s not even close”.
•Political scientists debate whether the mass public is as polarized as elites (elected officials, activists). Morris Fiorina argues that the American public is not as polarized as is often assumed, suggesting that elite polarization is wrongly imputed to the general public.
•Consistent with that, other work argues They argue that the mass public’s actual issue positions haven’t polarized nearly as much as that of the political elite. A book by Fiorina argues If we take the electorate as a whole—without slicing it by partisanship, region, or anything else—the public doesn’t look any different than it did in 1976. In this view, what looks like mass polarization is sorting — ideology and party identity aligning — rather than the public moving to extremes on issues, with affective polarization filtering down from elites.
In short: If measuring congressional voting, ideological gap between partisans, and mutual dislike, the current era is more polarized than any time since at least the 1870s-1920s and more than at any point in polling history since the 1970s-1990s. If measuring the entire sweep of American history including the Civil War, or measuring the average citizen's issue positions rather than elected officials and highly engaged partisans, scholars argue current polarization is not unprecedented.