“I don’t think we’ve seen the worst of it,” Douglas Ahler, a political scientist at Florida State University, emailed in response to my inquiry, adding:

When you take today’s urban-rural divide, couple it with the most engaged citizens’ tendency to live in echo chambers, and add accelerants in the forms of identity politics and misinformation campaigns, you have a house waiting to go up in flames.

“We identify three possible negative outcomes for democracy,” the political scientists Jennifer McCoy and Tahmina Rahman of Georgia State and Murat Somer of Koç University Istanbul, wrote in their 2018 paper, “Polarization and the Global Crisis of Democracy.”

The three negative outcomes, according to the authors, are gridlock; democratic erosion or collapse under new elites and dominant groups; and democratic erosion or collapse under old elites and dominant groups.

With few exceptions, political scientists are pessimistic about both the short- and long-term prospects for amelioration of hostile partisan division. It is probably best not to take comfort in experiments that reveal that, under certain circumstances, it is possible to lessen polarization.

Ethan Porter, a professor of media and public affairs at George Washington University, for example, wrote me that his work with Thomas J. Wood, a political scientist at Ohio State, shows that

when factual misinformation is corrected, people tend, on average, to be made more accurate. People are hardly invulnerable to factual corrections; on the contrary, whether Republicans or Democrats are exposed to corrections of their partisan leaders, they generally respond by becoming more accurate.

In practice, however, the rise of newspaper fact-checking would appear to at least partially achieve the goal of correcting misinformation, even as the rise of mutual hatred between Democrats and Republicans has accelerated.

Similarly, Joshua Kalla and David Broockman, political scientists at Yale and Berkeley, argued in their January 2020 paper “Reducing exclusionary attitudes through interpersonal conversation,” that “exclusionary attitudes — prejudice toward outgroups and opposition to policies that promote their well-being — are presenting challenges to democratic societies worldwide,” but, what they describe as “non-judgmentally exchanging narratives in interpersonal conversations can facilitate durable reductions in exclusionary attitudes.”

But, it is difficult, if not impossible, to conceive of circumstances under which Chuck Schumer and Mitch McConnell, or Nancy Pelosi and Donald Trump, would “non-judgmentally” exchange “narratives in interpersonal conversations.”

Nate Persily, a professor of law and political science at Stanford, wrote me that the most significant damage resulting from negative partisanship and polarization is

that the normal methods of accountability in a democratic society cease to apply. It used to be that people, regardless of party, believed government statistics about the employment rate and other metrics of progress and national well-being. Now, our interpretation of the basic facts of whether we are going in the right or wrong direction is dominated by whether expressing such an opinion is consistent with that which would advantage our tribe.

This extends to the legitimacy of elections, Persily continued, adding that

trust in the electoral process is now contingent on who wins. That is, losers will cry ‘fraud’ and consider the president illegitimate, even if the election is well-run. This is the kind of dynamic we see in the developing world and unstable democracies. It is a recipe for disaster.

Alex Theodoridis, a political scientist at the University of California-Merced, argued that instead of being an aberration, polarization may now be the norm, the default political environment:

Many look back fondly on the middle part of the last century when political party, ideology, and a host of social categories were not strongly aligned the way they are today and, thus, partisan polarization was far less pronounced.

But, he continued,

it is more likely that that bygone era was the aberration and today’s hyperpolarization is what we should expect in equilibrium. In other words, we probably ought to accept the current state of affairs as the new normal. The mutual dislike and distrust between Democrats and Republicans is likely to persist without a dramatic party realignment.

In fact, nothing would make Trump happier than to have Theodoridis’s belief that polarization is the new normal or to see Persily’s warnings of lost legitimacy proven true. Trump thrives when the climate is chaotic and disruptive and he is the prime example of lost legitimacy in American politics.