The predominant passion of all men in power,” wrote John Adams in 1787, “whether kings, nobles, or plebeians, is the same; that tyranny will be the effect, whoever are the governors…if uncontrolled by equal laws, made by common consent, and supported, protected, and enforced by three different orders of men in equilibrio.”

David S. Brown—in a new history of America’s “vital center”—thinks Adams is right: Tyranny is around the bend whenever a political system strays far from moderation. Far from serving as transitory players in factional struggles, or as foils for the ideologues who shaped history, those who have constituted the political center represent their own distinct political tradition. They have not only, Brown argues, “constituted a separate force in American politics,” but also “one that continues to inform and give substance to our ideological choices.”

Brown—the author of a biography of Richard Hofstadter—defines his moderate tradition in a distinct way: His vital centrists do not just seek the space between right and left, but also elevate politics above the interests of any single faction or group. Brown’s exemplars aren’t just squishes who split the difference. At their best, they’re swashbuckling pragmatists cutting through extremists’ cant, and in pursuit of America’s national interest.

Yet precisely because moderates see the dangers of a society that tips too far in any direction, moderation must assume a mask of tragedy. When confronted with the plural interests and freewheeling populism of mass democracy, moderates find that their vision of faction-less politics breaks down, and they face a choice: If they harness public opinion in service to the common good, they risk demagogy. If they reject popular politics altogether, they retreat into a curdled elitism. If they set the interests of one group over another, they flirt with the very politics they seek to oppose. In the central paradox of Brown’s book, moderates offer a modernizing politics, but they’re less sure about modernity. And so the story of America’s vital center is, in Brown’s telling, all at once a celebration of meliorist politics and a narrative of decline and fall.

Brown makes his case for the moderate tradition inductively. Rather than defend it from first principles, or trace centrist voters over time, he focuses on the politicians: in particular, six “moderate coalitions”: the Federalists in the Adams mold; the Democratic-Republicans in the Era of Good Feelings; early free-labor Republicans before the Civil War; reform-minded Republicans during the Gilded Age and Progressive Era; moderate GOP-ers from Wendell Willkie to Gerald Ford; and, a final twist, Democrats in the age of Obama—who, by Brown’s lights, also fall squarely within the Adams tradition of moderation. To tell this story, Brown strings together lively capsule portraits of John Adams, George Cabot, John Quincy Adams, Abraham Lincoln, Henry Adams, Theodore Roosevelt, William Howard Taft, and Henry Cabot Lodge Jr., before shifting to the two Bushes and the vital centrism of today’s Democrats.

As the list makes clear, Moderates isn’t quite what it seems: Brown isn’t doing intellectual and political portraiture for its own sake. His argument is for a certain kind of ideal political temperament that transcends any particular politician, period, or party; it is also for a certain kind of moderation that seeks to elevate politics above petty partisan divisions. Moderation, for Brown, is therefore not only a political tool but a good unto itself, and one that takes on many different manifestations along the way.

To make sense of this variegated tradition, Brown tries to establish three continuities among the moderates he considers. He wants to track the moderate temperament across time; he wants to outline the affinities between the intellectual habits of moderates and their practical politics; and he wants to relate political moderation to the ideological dead center in any given era.

The first task Brown handles largely by family resemblance, though he sometimes strains the parallels that connect his moderates, and the second task, the core of comparative biography, inevitably works better for some figures than others. Between the high art of statesmanship and the low art of majoritarian politics, Brown deems the former the true sign of moderate virtue. But it’s the third task where he is least successful, and where his defense of moderation begins to fall apart. Brown wants to keep his moderates at the center along a univariate dimension, but the players and ideologies keep changing, and so he wobbles around as to whether his moderate center is the center of the electorate or of the party in factional disputes or of some intellectual spat.

Perhaps some of the trouble comes from Brown’s vision of moderation. If the overall notion of political moderation can often feel like a moving target, its historical lineage, for Brown, is decidedly specific: It springs from Henry St. John, Viscount Bolingbroke. In a 1738 essay, Bolingbroke brought forth the supple and beguiling notion of the “Patriot King” whose political party would transcend particular interests and rule on behalf of the entire nation, “united by one common interest, and animated by one common spirit.” Though Bolingbroke accorded the word “moderate” no special significance, Brown takes this notion of a “Patriot King” as the germ of a politics that, he believes, has animated American public life from Adams to Obama.

The idea of governing for the sake of one nation has long been at the heart of the British Conservative Party, even down to the 1950s, when Rab Butler, who later became Harold Macmillan’s deputy prime minister, pointedly contrasted the supposed national interest of the Conservatives with the class interest of the Labour Party. But Brown is not interested in Bolingbroke’s British descendants so much as he is with his American ones. He quickly makes the Patriot King the avatar of an antiparty-ism that, from America’s founding, has fervently committed itself to the constitutional tradition and looked askance at popular politics.

For Brown, John Adams was the Patriot King par excellence. As he situated himself between the Jeffersonians and Hamiltonians, he exemplified moderation. He was sharply critical of the unfettered belief in human reason, which he saw in Thomas Paine (“a star of disaster”), but he was also forever on guard against the ill effects of speculators’ wealth, which distinguished him from Alexander Hamilton. Each, for Adams, threatened the balance and virtue that a civic community requires.

Brown persuasively links this vision of moderation to Lincoln, who, Brown argues, also sought a state that resisted predation “by either plutocracy or plantocracy.” But after Lincoln’s death, the moderate tradition that Brown depicts began to crack open. In America’s complex polity after the Civil War, moderation on issues of race, capitalism, and the contest between Democrats and Republicans often pointed in different directions. Nor—as the retreat of Henry Adams into his study in the face of America’s gilded excesses shows—did intellectual and political moderation necessarily go hand in hand. “As for traditions, constitution, principles, past professions and all that,” Adams wrote, lamenting the state of politics in his day, “the devil has put them back into his pocket.”

In the sordid world of Gilded Age politics, Northern moderates worried more about political corruption than about the bloody “Redemption” of the South. Men like Charles Francis Adams Jr. and E.L. Godkin, the founding editor of this magazine, also displayed rather immoderate support for the National Guard as it put down labor unrest.

As one moves through Brown’s book, one begins to realize that the various biographies offer few general lessons on how to choose among competing values, or how to distill the essence of the moderate tradition as a whole. The continuities among Brown’s vital centrists began to chafe against their discontinuities. Brown’s profiles also only spotlight distinguished moderates, thereby depicting their statesmanlike success, or in the case of Henry Adams, their noble failure, and as a result we miss the stories of moderate mediocrity. There’s no chapter, say, on Thomas Dewey.

In considering some of the other moderates in American politics that Brown has left out, the problems with viewing moderation as a coherent tradition becomes all the clearer. Political machines in cities, often with friendly partners at the state capitol, long exchanged tangible benefits—-turkeys at Thanksgiving, coal for immigrants’ stoves, paving contracts to contributors—in return for support. While the political boss may not have been a Patriot King, he was all the same a moderate in that he could only wield power if every element in his coalition was held “in equilibrio.”

Perhaps an even more damning example is the form of political moderation pursued by the Southern Democrats who dominated Congress for most of the 20th century and who, from the Federal Reserve Act of 1913 down through welfare reform in 1996, fundamentally shaped the American state. Like John Adams, the Southern Democrats feared wide-open politics and faraway bankers. But the end result was a sprawling national government that, directly and through the tax code, doles out benefits for the middle class, predominantly white, while relying on the states as intermediaries in stingy social programs aimed at the poor. Rather than pursuing the common interests of all Americans, their breed of political moderation meant racial subjugation, and Brown tellingly leaves them out of the story.

By the same token, Brown devotes great energy to the moderate sensibility, yet he has a much less precise sense of where and how, in the framers’ complex system, moderation might matter politically. The ambivalence starts with his view of political parties: Brown decries the blind loyalty of grubby wire-pullers, but he also looks askance at moderate Republicans who bolted for the Democrats in 1872 and 1884 and for Roosevelt’s Bull Moose in 1912. Nor does Brown’s vital centrism tell a consistent story about the presidency. The Adamses and George Cabot fretted about demagoguery, but Brown also cuts slack for Theodore Roosevelt, from whose rhetoric flows so many pathologies of a presidency that claims to speak alone for the people.

Above all, the central place where compromises happen in American politics—and where moderation is most essential—is in Congress, which Brown more or less ignores. John Quincy Adams’s finest days of moderation came, in Brown’s telling, while he served in the lowly House of Representatives, but after that, nobody Brown surveys had a congressional career that, on its own, amounted to anything. The moderate Republicans most important in Congress have been loners from the periphery, and they have proved thorns in the side of their own party. George W. Norris of Nebraska is the outstanding example, but Brown doesn’t say anything about him.

Brown closes out his old moderate lineage with Henry Cabot Lodge Jr., a more restrained figure than perhaps the more obvious choice of Nelson Rockefeller. The decision makes a certain poignant sense. Lodge burst onto the scene in 1936 when he nabbed a place in the Senate, at the age of 34, from the roguish governor, James Michael Curley; then, in 1952, having masterminded Dwight Eisenhower’s run for the presidency, he lost his seat to a very different Irishman, John F. Kennedy.

A firm Cold Warrior, Lodge served Ike at the United Nations, balanced Richard Nixon on the 1960 ticket, and twice headed to Saigon on diplomatic missions (shades of his grandfather’s imperialist mission). When Lyndon Johnson met with the so-called wise men in March 1968 to discuss the war, Lodge was a member of the delegation. By the time of his death in 1985, almost 39 years after he’d won his last election, Lodge’s moderate Republican Party had moved on. And so in Brown’s telling the moderate dream (at least among Republicans) perished not when Rockefeller infamously met his maker in the arms of his assistant, Megan Marshack, but in Beverly, Massachusetts—overlooking the waters where ships in the China trade once set sail—after Lodge died following a long illness.

Brown does append a penultimate chapter on what happened to Lodge’s party under the Bushes and a final one on the last three Democratic presidents. There’s a certain perverse pleasure, after a couple hundred pages spent with Brown’s brilliant grandees of moderation, to get a glimpse of the Bushes. Even in comparison with the Tafts, who also made money in the Ohio railroad boom, they look undistinguished: Prescott, who defended his view of Republican moderation as pure me-too-ism, proved to be every bit as much small and expedient as his son and grandsons. But it is the treatment of the Democrats, which concludes Brown’s book, that poses deeper problems to his argument. Jimmy Carter and Bill Clinton are the only Southerners in a book whose major subjects are Yankees, and Barack Obama, the most interesting of the bunch, gets a mere four pages, so we never really learn if Obama’s great dream of bipartisan unity carried with it anything more than faint echoes of the Patriot King.

Brown also offers little insight into the broader story of how the moderate elite, now largely ensconced in the Democratic Party, has been transformed in recent decades. Even if its members often still attend Harvard and Yale, the party’s moderates have become diversified, and with that diversity, they have absorbed the ideology of meritocracy to buttress their claim to power. The old qualms about mass politics have also returned to the fore, now encased in an economistic technocracy.

The current president’s name appears nowhere in Moderates, as the book was written before his victory, but its heroes anticipated him. John Adams condemned “landjobbing” and Theodore Roosevelt those rich men “purely of the glorified huckster or the glorified pawnbroker type.” Republicans may one day seek an identity beyond tax cuts and resource extraction and embrace something other than the Reagan mythos when they look for a usable past. But Republican moderates are, three senators’ votes on health care notwithstanding, in short supply. Whether they fear a primary challenger or whether they don’t much mind Trump is hardly the point: Events have borne out Brown’s longer story on the decline of moderation, at least in the Republican Party. Republicans may direct their gaze to figures like Alexander Hamilton, Henry Clay, and William McKinley, but the party that long served as home to Brown’s vital centrists is Donald Trump’s now. The last threads that tied it to the moderate tradition have snapped.