“Democracy is a system in which parties lose elections,” Adam Przeworski, a political scientist at N.Y.U., wrote in 1991 — a definition that would prove prescient in the wake of the 2020 election.“Outcomes of the democratic process are uncertain, indeterminate ex ante,” Przeworski continued. “There is competition, organized by rules. And there are periodic winners and losers.”Presumably, Donald Trump has no idea who Adam Przeworski is, but Trump refused to accept the Przeworski dictum in the aftermath of his 2020 defeat, claiming victory despite all evidence to the contrary.Trump’s success in persuading a majority of Republicans of the legitimacy of his palpably false claims has revealed the vulnerability of American institutions to a subversion of democratic norms. That much is well known.These questions were gaining salience even before the 2020 election. As Lilliana Mason, a political scientist at Johns Hopkins, explains in her 2018 book, “Uncivil Agreement: How Politics Became Our Identity”:The election of Trump is the culmination of a process by which the American electorate has become deeply socially divided along partisan lines. As the parties have grown racially, religiously, and socially distant from one another, a new kind of social discord has been growing. The increasing political divide has allowed political, public, electoral, and national norms to be broken with little to no consequence. The norms of racial, religious, and cultural respect have deteriorated. Partisan battles have helped organize Americans’ distrust for “the other” in politically powerful ways. In this political environment, a candidate who picks up the banner of “us versus them” and “winning versus losing” is almost guaranteed to tap into a current of resentment and anger across racial, religious, and cultural lines, which have recently divided neatly by party.Most recently, these questions have been pushed to the fore by two political scientists at Harvard, Steven Levitsky and Daniel Ziblatt, who published “Tyranny of the Minority” a month ago.Their thesis:By 2016, America was on the brink of a genuinely multiracial democracy — one that could serve as a model for diverse societies across the world. But just as this new democratic experiment was beginning to take root, America experienced an authoritarian backlash so fierce that it shook the foundations of the republic, leaving our allies across the world worried about whether the country had any democratic future at all.This authoritarian backlash, Levitsky and Ziblatt write, “leads us to another unsettling truth. Part of the problem we face today lies in something many of us venerate: our Constitution.”Flaws in the Constitution, they argue,now imperil our democracy. Designed in a pre-democratic era, the U.S. Constitution allows partisan minorities to routinely thwart majorities, and sometimes even govern them. Institutions that empower partisan minorities can become instruments of minority rule. And they are especially dangerous when they are in the hands of extremist or antidemocratic partisan minorities.The Levitsky and Ziblatt thesis has both strong supporters and strong critics.In an essay published this month, “Vetocracy and the Decline of American Global Power: Minority Rule Is the Order in American Politics Today,” Francis Fukuyama, a senior fellow at Stanford’s Freeman Spogli Institute for International Studies, argues:America has become a vetocracy, or rule by veto. Its political system spreads power out very broadly, in ways that give many individual players the power to stop things. By contrast it provides few mechanisms to force collective decisions reflecting the will of the majority.When combined with the extreme degree of polarization in the underlying society, Fukuyama goes on, “this leads to total gridlock where basic functions of government like deliberating on and passing yearly budgets become nearly impossible.”Fukuyama cites the ongoing struggle of House Republicans to elect a speaker — with the far-right faction dead set against a centrist choice — as a case study of vetocracy at work:The ability of a single extremist member of the House to topple the speaker and shut down Congress’ ability to legislate is not the only manifestation of vetocracy on display in 2023. The Senate has a rule that gives any individual senator the right to in effect block any executive branch appointment for any reason.In addition, the Senate requires “a supermajority of 60 votes to call the question, making routine legislating very difficult.”I asked Fukuyama whether America’s current problems stem, to some extent, from the constitutional protection of the interests of minority factions (meant here the way it’s used in Federalist 10).He replied by email: “The large numbers of checks and balances built into our system did not present insuperable obstacles to governance until the deepening of polarization in the mid-1990s.”Sanford Levinson, a law professor at the University of Texas, makes a different argument: “I think that our current problems are directly traceable to deficiencies in the formal structures of the American political system as set out in 1787 and too infrequently amended thereafter.”In his 2008 book, “Our Undemocratic Constitution,” Levinson writes, “I have become ever more despondent about many structural provisions of the Constitution that place almost insurmountable barriers in the way of any acceptable notion of democracy.”In support of his thesis, Levinson asks readers to respond to a series of questions “by way of preparing yourself to scrutinize the adequacy of today’s Constitution”:Do you support giving Wyoming the same number of votes in the Senate as California which has roughly seventy times the population? Are you comfortable with an Electoral College that has regularly placed in the White House candidates who did not get a majority and, in at least two — now three — cases over the past 50 years did not even come in first? Are you concerned that the president might have too much power, whether to spy on Americans without any congressional or judicial authorization or to frustrate the will of the majority of both houses of Congress by vetoing legislation with which he disagrees on political ground?Pessimistic assessments of the capacity of the American political system to withstand extremist challenge are by no means ubiquitous among the nation’s scholars; many point to the strength of the judiciary in rejecting the Trump campaign’s claims of election fraud and to the 2022 defeat of prominent proponents of “the big lie.” In this view, the system of checks and balances is still working.Kurt Weyland, a political scientist at the University of Texas-Austin, is the author of the forthcoming book “Democracy’s Resilience to Populism’s Threat.” Weyland contended by email that instead of treating the “United States’ counter-majoritarian institutions as a big problem, firm checks and balances have served as a safeguard against the very real threats posed by Trump’s populism.”Weyland continued:Without independent and powerful courts; without independent state and city governments; without federalism, which precluded central-gov’t interference in the electoral system; and without a bicameral congress, in which even Republicans slowed down Trump by dragging their feet; without all these aspects of US counter-majoritarianism, Trump could have done significantly more damage to U.S. democracy.Polarization, Wayland argued, is a double-edged sword:In a counter-majoritarian system, it brings stalemate and gridlock that allows a populist leader like Trump to claim, “Only I can do it,” namely cut through this Gordian knot, with “highly problematic” miracle cures like “Build the Wall.’ ”But at the same time, Weyland continued,Polarization has one — unexpected — beneficial effect, namely, to severely limit the popular support that Trump could ever win: Very few Democrats would ever support him! Thus, whereas other undemocratic populists like Peru’s Fujimori, Venezuela’s Chavez, or now El Salvador’s Bukele won overwhelming mass support — 70-90 percent approval — and used it to push aside liberal obstacles to their insatiable power hunger, Trump never even reached 50 percent. A populist who’s not very popular simply cannot do that much damage to democracy.Along similar lines, Frances Lee, a political scientist at Princeton, argues in a 2019 paper, “Populism and the American Party System: Opportunities and Constraints,” that compared with most other democracies, “the U.S. system offers much less opportunity for organized populist parties but more opportunity for populist candidacies.”The two major parties, Lee continues, are more “vulnerable to populist insurgency than at other points in U.S. history because of (1) changes in communications technology, (2) the unpopularity of mainstream parties and party leaders and (3) representation gaps created by an increasingly racialized party system.”At the same time, according to Lee, “the U.S. constitutional system impedes authoritarian populism, just as it obstructs party power generally. But the vulnerability of the major parties to populist insurgency poses a threat to liberal democratic norms in the United States, just as it does elsewhere.”American public opinion, in Lee’s view, “cannot be relied on as a bulwark of liberal rights capable of resisting populism’s tendencies toward authoritarianism and anti-pluralism.”While the U.S. electoral system “has long been unfavorable to insurgent or third parties, including populist parties,” Lee writes, the avenue to political power lies in the primary nomination process:The American system of nominations subjects the major parties to radically open internal competition through primary elections. The combined result of these electoral rules is that populists win more favorable outcomes in intraparty competition than in interparty competition.In one area of agreement with Levitsky and Ziblatt, Lee makes the case that the diminishing — that is, veiled — emphasis of previous generations of Republican leaders on divisive issues of race, ethnicity and immigration provided a crucial opening for Trump.“Before 2016, the national leadership of the Republican and Democratic Parties had been trending toward closer convergence on policy issues relating to race and ethnicity, both in terms of party positions and rhetoric,” she writes, adding that “before 2016, the two parties also did not offer clear alternatives on immigration.”This shift to a covert rather than an overt approach to racial issues created an opening for Trump to run as a broadly “anti-elite” candidate representing the views of the white working class.“Willing to violate norms against the use of racialized rhetoric, Trump was able to offer primary voters a product that other Republican elites refused to supply,” Lee writes. “Those appeals strengthened his populist, anti-elite credentials and probably contributed to his success in winning the nomination.”There is a third line of analysis that places a strong emphasis on the economic upheaval produced by the transition from a manufacturing economy to a technologically based knowledge economy.In their June 2023 article “The Revival of U.S. Populism: How 39 Years of Manufacturing Losses and Educational Gains Reshaped the Electoral Map,” Scott Abrahams and Frank Levy, economists at Louisiana State University and M.I.T., make the case that polarization and institutional gridlock have roots dating back more than four decades:The current revival of right-wing populism in the United States reaches back to 1980, a year that marked a broad shift in national production and the demand for labor. In that year, manufacturing employment began a long decline and the wage gap between college and high school graduates began a long expansion.The result, Abrahams and Levy contend:was a growing geographic alignment of income, educational attainment and, increasingly, cultural values. The alignment reinforced urban/rural and coastal/interior distinctions and contributed to both the politicization of a four-year college degree and the perception of educated “elites” or “coastal elites” — central parts of today’s populist rhetoric.Abrahams and Levy conclude: “If our argument is correct, it has taken almost 40 years to reach our current level of polarization. If history is a guide, it won’t quickly disappear.”Herbert Kitschelt, a political scientist at Duke, argued in an email that the strains on the American political system grow out of the interaction between divisive economic and cultural trends and the empowerment of racial and ethnic minorities: “The inevitable emerging socio-economic divisions in the transition to knowledge societies — propelled by capitalist creative destruction — and the sociocultural kinship divisions develop a politically explosive stew due to the nature of U.S. political institutions.”On one side, Kitschelt wrote, “Technological innovation and economic demand patterns have led to a substitution of humans in routine tasks jobs by ‘code’ and machines — whether in manufacturing or services/white collar occupations. These precipitate wage stagnation and decline.”On the other side, “There is a revolution of kinship relations that got underway with the access of women to higher education in the 1950s and 1960s. This has led to a questioning of traditional paternalistic family relations and triggered a reframing of gender conceptions and relations, as well as the nature and significance of procreation and socialization of the next generation.”The interaction, Kitschelt continued, “of socio-economic anxiety-promoting decline amplified by rapid demographic erosion of the share of white Anglo-Saxon ethnics, and cultural stress due to challenges of paternalist kinship relations and advances of secularization have given rise to the toxic amalgam of white Christian nationalism. It has become a backbone and transmission belt of right-wing populism in the U.S.”At the same time, Kitschelt acknowledged, “Levitsky and Ziblatt are absolutely right that it is the circumstances of enslavement at the founding moment of U.S. independence and democracy that created a system of governance that enable a determined minority (the enslavers) to maintain a status quo of domination, exploitation, and dehumanization of a whole tier of members of society which could not be undone within the locked-in web of institutional rules.”To support his argument, Kitschelt cited “the process in which Trump was chosen as U.S. president”:Roughly 10 percent of registered voters nationwide participated in the Republican presidential primaries in 2016. The plurality primary winner, Donald Trump, rallied just 3-5 percent of U.S. registered voters to endorse his candidacy and thereby sail on to the Republican Party nomination. These 3-5 percent of the U.S. registered voters — or 2-4 percent of the U.S. adult residential population — then made it possible for Trump to lose the popular vote but win the Electoral College majority.All of which gets us back to the Przeworski dictum with which I began this column, that “democracy is a system in which parties lose elections.”Przeworski’s claim, Henry Farrell, a political scientist at Johns Hopkins, writes in an essay published last month, “inspired a lot of political scientists to use game theory to determine the conditions under which democracy was ‘self-enforcing’: that is, how everyone’s beliefs and actions might line up to make democracy a self-fulfilling prophecy.”At the same time, Farrell continues, “his argument powerfully suggests a theory of democratic fragility, too.” What happens when “some powerful organized force, such as a political party, may look to overturn democratic outcomes” or “such a force may look to ‘drastically reduce the confidence of other actors in democratic institutions’”?At that point, as the two parties react to each other, Farrell suggests, “democracy can become self-unraveling rather than self-enforcing”:If you (as say the leader of the Republican Party) look to overturn an election result through encouraging your supporters to invade the U.S. Capitol, and claim that the election was a con, then I (as a Democratic Party leader) am plausibly going to guess that my chances of ever getting elected again will shrivel into nonexistence if you gain political power again and are able to rig the system. That may lead me to be less willing to play by the rules, leading to further collapse of confidence on your part and so on, in a downward spiral.In other words, with a majority of Republicans aligned with an authoritarian leader, Democrats will be the group to watch if Trump wins re-election in November 2024, especially so if Republicans win control of both the House and Senate.While such a turn of events would replicate the 2016 election results, Democrats now know much more about what an across-the-board Republican victory would mean as Trump and his allies have more or less announced their plans for 2025 if they win in 2024: the empowerment of a party determined to politicize the civil service, a party committed to use the Department of Justice and other agencies to punish Democrats, a party prepared to change the rules of elections to guarantee the retention of its majorities.In a report last month, “24 for ’24: Urgent Recommendations in Law, Media, Politics and Tech for Fair and Legitimate 2024 U.S. Elections,” an ad hoc committee convened by the Safeguarding Democracy Project and U.C.L.A. Law School warned:“The 2020 elections confirmed that confidence in the fairness and legitimacy of the election system in the United States can no longer be taken for granted. Without the losing side accepting the results of a fair election as legitimate, the social fabric that holds democracy together can fray or tear.”The Times is committed to publishing a diversity of letters to the editor. We’d like to hear what you think about this or any of our articles. Here are some tips. And here’s our email: letters@nytimes.com.Follow The New York Times Opinion section on Facebook, Twitter (@NYTopinion) and Instagram. More