James T. Kloppenberg, author of “Toward Democracy: The Struggle for Self-Rule in European and American Thought,” teaches U.S. history at Harvard.

When Ringling Brothers closed down in the spring of 2017, most people blamed its demise on new forms of entertainment. Only a few tied it to the circus that had set up shop in the White House. The ringmaster there cut his teeth on “the art of the deal” (a.k.a. swindling, debt dodging and tax evasion) before honing his act through tawdry made-for-tabloid scandals, the cesspool of professional wrestling and the carefully scripted faux spontaneity of “reality television.” Lions, tigers and bears could not compete with his lies, tweets and boasts. In his presidency, Donald Trump has continued to toy with the public, proclaiming one outrageous falsehood after another and denouncing American institutions such as the judiciary, the press, the opposition party, the FBI and anyone brave enough to insist that truths exist independent of his bluster. Fortunately, despite the president’s admiration for

Vladimir Putin and Kim Jong Un, and despite the Republican Party’s complicity in his efforts to establish an authoritarian regime in the United States, he has failed to silence journalists, Democrats and courageous people unintimidated by his bullying and unafraid of his mockery.

At a time of heightened emotions and anxiety, we are fortunate to have responsible reporters such as Greg Sargent. Known to many for his Plum Line blog in The Washington Post, Sargent has produced a clear, insightful account of our current condition, informed by impressive immersion in the best work of political scientists as well as investigative journalists. In “An Uncivil War,” he directs readers’ attention away from the president’s daily descent into the muck of insult and examines the structural problems of 21st-century politics. Unless the American people take action at the ballot box, these problems, which made possible a Trump presidency and a Senate willing to confirm Brett Kavanaugh to the Supreme Court, will persist long after Trump’s circus leaves town.

Sargent deftly presents the evidence necessary to expose Republicans’ baseless claims of voter fraud, a threat fabricated to justify voter suppression laws, adopted in many states, that disfranchise the poor, nonwhites, recent immigrants and others likelier to vote for Democratic candidates. Sargent shows why the demography of 21st-century America, which has recently yielded aggregate majority votes for Democrats, has nevertheless worked in favor of Republicans. First, because Democrats cluster in cities, many of their votes are “wasted” in overwhelmingly Democratic legislative districts, while more sparsely populated rural areas send a majority of Republicans to state legislatures, the House and especially the Senate, where states such as Wyoming (whose population is less than 600,000) have as much clout at California (more than 39 million). Second, the increasingly sophisticated techniques of gerrymandering state legislative and congressional districts has made it possible for Republicans since the 2010 Census to consistently win a higher percentage of seats than votes. This “countermajoritarian” outcome is no accident. It results instead, Sargent demonstrates, from a self-conscious strategy adopted by Republican Party funders, who invested heavily in state legislative and gubernatorial contests that the Democratic Party all but ignored. Until Democrats address these problems, hysterical cries of voter fraud will continue to justify voter suppression, and gerrymandering by Republican state lawmakers will continue to generate a GOP-dominated House and Senate.

Even more alarming is the other principal focus of Sargent’s “Uncivil War”: the disinformation campaign that conservatives have mounted in recent decades on television, radio and digital media. As Walter Lippmann first argued in “Public Opinion” (1922), people in mass societies interpret the modern world through the “pictures” and “fictions” in their heads. The “pseudo-environments” they inhabit are made comprehensible only through the “stereotypes” that enable them to make sense of an otherwise chaotic reality, and for that reason citizens are more susceptible than ever to advertising and propaganda.

Disregard for truth has been central to authoritarian governments since the 1930s, when totalitarian regimes manipulated the public by controlling access to information and silencing those who dared protest. That strategy has now matured in the United States, where countless falsehoods masquerade as truth 24/7 on Fox News Channel and in the ever-expanding right-wing blogosphere. These distortions are deliberate. They are calculated to create a fact-free world in which there are only opinions, the louder and more melodramatically shouted, the better. The reason Trump constantly demonizes the media, he told Lesley Stahl of “60 Minutes” in a moment of remarkable candor, is “to discredit you all and demean you all so when you write negative stories about me, no one will believe you.” Whether or not readers of “An Uncivil War” reconsider Hillary Clinton’s 1998 claim about “a vast right-wing conspiracy,” they will see that the strategies of the unscrupulous have grown more sophisticated and dangerous, as the results of the 2016 presidential election confirmed.

Having shown that Republicans have self-consciously gamed electoral politics and cynically manipulated public opinion, Sargent shifts gears. He reflects on the consequences for U.S. politics of the scorched-earth tactics that have become common since House Speaker Newt Gingrich first shut down the government in the 1990s. Playing “constitutional hardball,” a term Sargent adopts from legal scholar Mark Tushnet, has tempted American politicians since the 1790s. Until now, however, hyperpartisanship has always given way to less rancorous, if hardly harmonious, periods when bipartisanship was possible.

For more than two decades, Republicans have treated Democrats as enemies of the American people. Efforts to find compromise, such as Barack Obama’s adoption of a health insurance plan devised by the American Enterprise Institute and implemented by Massachusetts Gov. Mitt Romney, have been dismissed with contempt. In an unprecedented move, consistent with the Republicans’ sudden reliance on filibusters to block judicial appointments during Obama’s presidency, Obama’s Supreme Court nominee, Merrick Garland, was refused even a Senate hearing. Voters, Senate Majority Leader Mitch McConnell declared, should make the decision at the ballot box a year later. With another election in just a few weeks, McConnell decided the decision was up to Senate Republicans, not the fickle public, which might have been swayed by a thorough investigation of the serious allegations against Kavanaugh.

American democracy depends on the willingness of the people to trust the legitimacy of our institutions and the integrity of elected officials. The president’s egregious self-dealing and norm-busting as well as the refusal of Republican members of Congress since 1994 to follow the customary rules of engagement have eroded that trust. Sargent concludes “An Uncivil War” by urging caution on the part of those Democrats inclined to fight fire with fire, to seek power by any means necessary and to work just as hard to undermine democratic procedures as Republicans have done in recent decades. Mutual respect and a willingness to accept disagreement are indispensable qualities for self-government. “An Uncivil War” merits wide readership, not only because of Sargent’s persuasive indictment of the anti-democratic, countermajoritarian and cynical strategies Republicans have employed for decades, but also because of his well-reasoned arguments for continuing to play by — instead of bending — the rules.

An Uncivil War

Taking Back Our Democracy in an Age of Trumpian Disinformation and Thunderdome Politics

By Greg Sargent

Custom House. 246 pp. $26.99