Donald Trump caught academics off guard. Historians and social scientists had long studied the American right, amassing a vast library on its relationship to race, gender, sex, the media, the Cold War, religion, and big and small business. Less explored was the role of the Constitution, which has always been more friend than foe to the American way of repression. This gap in the literature left the field wide open for experts in authoritarianism abroad and scholars of authoritarianism past.

The most important contribution to this genre was “How Democracies Die,” by the Harvard political scientists Steven Levitsky and Daniel Ziblatt. Studying how democracy was undermined elsewhere, Levitsky and Ziblatt defined the threat of Trumpism as an attack on the Constitution, the rule of law, and institutions. They also claimed that these pillars were less sturdy than people supposed. The Constitution was riddled with holes. Restrictions on Presidential prerogatives were not written down. Institutions designed to check extremists, whether specified in the text (a bicameral legislature) or not (political parties), were vulnerable to extremists.

Most worrisome of all, the ligaments joining these parts, what Levitsky and Ziblatt called “norms,” were frayed. Two norms in particular—tolerance of one’s opponents and forbearance in the exercise of power—were foundational to constitutional democracy. But since 1965, 1994, or 2010 (Levitsky and Ziblatt never settled on a date), those norms had been eroding. Traditionally, élite “gatekeepers” had been the custodians of norms, exercising “peer review” over norm eroders such as Charles Lindbergh and George Wallace. But, in the wake of reforms initiated by the Democrats after 1968 (another date), and later copied by the Republicans, ordinary voters, rather than insider élites, were empowered to choose the Presidential ticket of each party. For a while, the establishment held the line against outsiders. Then came 2016, when Republican leaders failed to stop Trump and rallied behind him.

Within a month of its publication, in January, 2018, “How Democracies Die” hit the Times best-seller list. It’s easy to see why. The book gave voice to liberals who felt betrayed not by their country but by its voters, the gate-crashers who put Trump into power. Levitsky and Ziblatt’s readers believed in norms, trusted élites, and valued institutions, particularly the Supreme Court. They revered the Constitution. The problem was the half of the country that didn’t.

But spring came, as it does, and a new wind began to blow on the left. After the confirmation of Brett Kavanaugh, Neil Gorsuch, and Amy Coney Barrett, progressives started seeing the Court less as a counter to Trumpism than as its conduit. “Defend institutions” may have made sense at the beginning of Trump’s reign. By the end, it sounded like a call to protect the Electoral College and other struts of the right. In 2018, Levitsky and Ziblatt had recommended building coalitions with “red-state Republicans,” abandoning abortion as a litmus test for candidates, and making unnamed but “tough” concessions to moderate voters. Now liberals were ready to play hardball: abolish the filibuster, pack the Court, admit new states to increase Democratic votes in the Senate, and stop all coöperation with the G.O.P.

None of this agenda has been enacted, but its pressures are felt throughout “Tyranny of the Minority,” Levitsky and Ziblatt’s follow-up to “How Democracies Die.” There’s little talk of norms in the new volume. Instead, Levitsky and Ziblatt reaffirm the call to end the filibuster and remake the Court, norm-eroding measures they previously cautioned against. More surprising is their revised view of democracy itself. The primary threat to the system is no longer demagogues; it’s the very institutions that Levitsky and Ziblatt once rallied readers to protect. If the United States is to remain—really, become—a democracy, Americans must stop treating its founding text “as if it were a sacred document.” The Constitution, the deepest norm in American politics, must be eroded.

In 1857, the British historian and statesman Thomas Macaulay set out a grim forecast for the United States. In Britain, political power was safely tucked away in the pockets of élites, who were “deeply interested in the security of property.” America had foolishly handed power to the “discontented” masses. For now, there was land for them to settle in the West. But, when that safety valve failed, the working classes, “none of whom has had more than half a breakfast, or expects to have more than half a dinner,” would vote to strip the minority of their wealth. The Constitution wouldn’t stop them. It was “all sail and no anchor.”

For much of American history, it’s been the reverse: all anchor, no sail. The most influential authors of the Constitution were terrified of democratic majorities. They devised a government with a sluice of filters—at least six, which Levitsky and Ziblatt note is “an unusually large number”—to push majorities to the side. More than two centuries later, we still have this “uniquely counter-majoritarian democracy,” which is hardly a democracy at all.

Congress has two of the filters. A bicameral legislature is one; the Senate is the other. Many countries have learned that, in a real democracy, upper chambers either don’t exist or have highly limited powers. The U.S. Senate doesn’t just have power equal to (and, in some cases, greater than) the House; it also represents states rather than individuals. Wyoming, with a population of about five hundred and eighty thousand, has as many votes as California, which has nearly forty million people. There’s a reason that most democracies don’t operate in this way: it’s undemocratic. This has been apparent for centuries. All of the antislavery bills that passed the House between 1800 and 1860 were killed by the minoritarian Senate.

If the House and the Senate agree on a bill, they still need the approval of the President, who’s elected not by the voters but by the Electoral College. That’s the third filter. With a bias toward smaller states and a winner-take-all structure, the Electoral College can send the loser of the popular vote to the White House. In this century alone, that’s happened twice.

Even if the elected branches agree on a bill, the Supreme Court can strike it down. Justices are put on the bench by the Senate and the President, so we can have a Supreme Court majority, like the one we have now, created by a combination of Presidents who lost the popular vote and senators who represent a minority of the voters. That’s the fourth filter, a creature of the preceding three.

Meanwhile, another course runs parallel to the national one. Our federal system, the fifth filter, grants states tremendous power, including the right to design electoral rules—how district lines are drawn, who can access the ballot, how elections are conducted, and so on—that privilege minorities over majorities. Between 1968 and 2016, the party with fewer votes has won a state house a hundred and twenty-one times and a state senate a hundred and forty-six times. Those legislatures, in turn, can gerrymander federal election districts, turning the putatively majoritarian House into another counter-majoritarian chamber. They also can pass laws, such as bans on abortion, that abridge the most basic freedoms of the people.

Many nations entered the twentieth century saddled with the yoke of counter-majoritarianism. They got rid of it. We haven’t, thanks to our mega-counter-majoritarian requirement for constitutional change, which is the sixth and most important filter. Two-thirds of both houses in Congress propose an amendment, and three-fourths of the states must then ratify it. According to Levitsky and Ziblatt, a political scientist has devised something called the Index of Difficulty to measure how hard it is to change a country’s constitution. Ours tops the list, by a wide margin.

This news comes at a bad time. Today’s Republicans—many of them white and living in rural areas—hold fast to the Constitution for protection against Democratic majorities. Those majorities increasingly live in large cities, where the jobs are, and many of those cities are in highly populated, Democratic states. The combination of these factors leaves blue voters vulnerable to malapportionment in the states, where they needlessly pile up their votes in cities, and in the Senate and Electoral College. A minority of voters can now inflict a legislative wallop of racism, sexism, nativism, homophobia, transphobia, and economic misery on the rest of us—and never have to pay for it at the polls.

This is the “tyranny of the minority” that Levitsky and Ziblatt rightly fear. No lawless strongman or populist autocracy, it’s a product of the very Constitution that we have been taught to admire.

Once we set aside the compass of the Constitution, where should we look for our North Star? Levitsky and Ziblatt point to “multiracial democracy.” Either we become a multiracial democracy or we cease to “be a democracy at all.” The battle, in other words, is existential.

Yet Levitsky and Ziblatt aren’t equipped for war. Like many analysts, they believe that today’s right is driven by a primitive fear. Conservative voters fear the simple fact of demographic change. As immigrants, people of color, women, and sexual and gender minorities assume greater visibility, dominant groups—straight, white, cis, native-born men—fear a loss of status. That fear of erasure fuels the G.O.P.’s “turn to authoritarianism.” Holding on to government power is an “existential” imperative for the Party and the groups it represents.

This argument, now ubiquitous on the left, has come to seem like a natural law of the political universe, describing our most elemental drives of identity and anxiety. It makes sense that conservatives would believe it, as they’ve been pushing it since the French Revolution. But it poses a problem for the left, and for Levitsky and Ziblatt, in particular.