Is political polarization worse than it's been in the past?

Your question is timely — I'll gather recent data comparing today's polarization to past eras.

Yes and no — it depends on what timeframe and what kind of polarization you mean.

1. By modern measures, yes — the last 50-150 years is near a peak

Affective polarization — how much partisans dislike and distrust the opposing party — is at historically high levels in the US.

Ideological / congressional polarization is also at a modern high:

> Indeed, 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.
> It’s become commonplace among observers of U.S. politics to decry partisan polarization in Congress. Indeed, 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 measure used is DW-NOMINATE, which uses lawmakers' roll-call votes to place them on a liberal-conservative scale.

Pew's analysis of that data found:

> There are now only about two dozen moderate Democrats and Republicans left on Capitol Hill, versus more than 160 in 1971-72.

> Between the 92nd Congress of 1971-72 and the current 117th Congress, both parties in both the House and the Senate have shifted further away from the center, but Republicans more so. House Democrats, for example, moved from about -0.31 to -0.38... House Republicans, by contrast, moved from 0.25 to nearly 0.51.

The common ground has effectively vanished:

> Five decades ago, 144 House Republicans were less conservative than the most conservative Democrat, and 52 House Democrats were less liberal than the most liberal Republican.

> Since 2002, when Republican Rep. Constance Morella of Maryland was defeated for reelection and GOP Rep. Benjamin Gilman of New York 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.

By that metric, the US is also an outlier internationally:

> Political polarization is higher in the United States than in any other advanced country for which we have comparable data.

2. By the sweep of American history, no — the Civil War era and 1960s were worse

Historians caution against saying 2020s America is the most divided ever.

> As a historian who has written and taught about the Civil War era for several decades, I know that current divisions pale in comparison to those of the mid-19th century.

> Between Abraham Lincoln’s election in November 1860 and the surrender of Robert E. Lee’s Confederate army at Appomattox in April 1865, the nation literally broke apart.

That period saw:

> To compare anything that has transpired in the past few years to this cataclysmic upheaval represents a spectacular lack of understanding about American history.

> No political issue in 2020 approaches slavery in the mid-19th century in terms of potential divisiveness.

Other periods of sustained violence were also more intense than today:

> The United States has gone through periods of far more sustained political violence, including the Civil War era, Reconstruction, the assassinations and racial violence of the 1960s, and earlier waves of extremist activity.

> With that said, the amount of violence we are witnessing is not as bad as the 1960s and 1860s.

> Political polarization is not always worse than it’s ever been. Riots raged across America in the 1960’s in response to racial injustice.

3. Why it feels worse now

Researchers distinguish two types:

> Affective polarisation — how much partisans dislike and distrust the opposing party — is at historically high levels in the US and rising in many other democracies. Policy polarisation — how far apart parties are on actual policy positions — is more complex: elites are highly polarised, but mass opinion on many specific policies shows more overlap than the culture war framing suggests.

In other words:

So the short answer: