The bloodletting this week at the New Republic—the journal of opinion regarded for a century as the flagship of American liberalism—has been rightly taken to herald the end of a great magazine. With the news that its two top editors, Frank Foer and Leon Wieseltier, resigned, that much of the staff subsequently quit, and that the magazine will halve its yearly output and move its headquarters from Washington to New York, the political and intellectual worlds are thrumming with outrage toward the short-sightedness of the magazine’s new leadership and elegies for an august institution.

As a former staffer and (until Friday) contributing editor, I share the sadness. But one reason for the New Republic’s demise has not been fully appreciated, and that has to do with its unique tradition of heterodox liberalism. The New Republic is being seen as a casualty of the crisis of print journalism that has felled many other newspapers and magazines during the past decade—the drying up of advertising revenue amid free and cheap online commentary. The problem with this line of argument is that “little magazines” have always lost money, relying instead on the largesse of rich owners, whose combination of public-spiritedness and vanity has led them to sponsor high-quality journalism. The New Republic was hurt by something more specific: the polarization of a media environment that leaves little room for a strain of liberal thought that not only attacks the right and the far left but also prods and questions liberalism itself.

Founded in 1914 by some of the leading minds of the Progressive Era—Herbert Croly, Walter Lippmann, and Walter Weyl—the New Republic from the beginning sought to challenge conventional thinking, including among its own readership. These editors recognized that while liberalism (like all political creeds) needs foundational principles, one of those principles specific to liberalism is openness to debate, experiment, and reconsideration. Dogmatism, even more than conservatism, was its bête noire.

Over the years the magazine sometimes wavered in that mission. During the editorial tenure of former Vice President Henry Wallace in the 1940s, it descended into high-minded cliché, and for spells in the postwar years, it lapsed into sleepy predictability. But with its purchase by Harvard professor Martin Peretz in the mid-1970s, the New Republic regained its stature as the most provocative magazine on the left. Peretz hired a bevy of brilliant young minds. Three in particular became the three finest editors of their generation: Michael Kinsley, Hendrik Hertzberg, and Wieseltier. The twentysomethings who cut their teeth at the magazine in these decades include some of the most accomplished nonfiction writers working today.

As important, the magazine played a key role in revitalizing American liberalism. When Peretz bought the New Republic, the left was on the ropes. The 1960s had been great years of progressive achievement, but in the 1970s, voters were growing disaffected from the Democratic Party, which failed to develop new ideas to meet the challenges of a changing economy and a turbulent world. Liberal thinking ossified. When I was growing up, the adjective that most often preceded “liberal” was “knee-jerk.”

Under Peretz and his editors, the magazine led the way in questioning left-wing shibboleths on issues such as crime and fiscal policy and especially foreign policy, where it championed a revival of the liberal internationalism that had guided the Democratic Party from Woodrow Wilson through John F. Kennedy, until the disaster of Vietnam. The election in 1992 of Bill Clinton, whose candidacy the magazine supported early on, marked a triumph of this reconstructed liberalism.

Some old-time subscribers and confirmed partisans disliked the magazine for its willingness to publish conservative voices—Fred Barnes was its ace White House correspondent for years while staff writer Charles Krauthammer migrated during his time at the magazine from Walter Mondale speechwriter to neoconservative paragon. Critics assailed its perceived hawkishness and its unapologetic Zionism, which had long been anathema to the hard left and was now becoming distasteful to certain high-minded progressives as well.

But to other readers, the sense of freewheeling debate—as opposed to bien-pensant wisdom or party-line doctrine—gave the magazine its exciting appeal. As a college student in the late 1980s, I found its pages more stimulating than those of rival publications, which tended to toe what was already being called the “politically correct” line. I never agreed with all of the magazine’s positions—its support of the Nicaraguan contras, its opposition to affirmative action—but its pieces made me think in ways that few newspaper columnists or television pundits did. Beyond affording the pleasures of contrarianism, this breed of journalism honored the journalistic imperative to comfort the afflicted and afflict the comfortable. Who, after all, was more comfortable than one’s own loyal readers?

The New Republic’s heterodox liberalism—the willingness (indeed the eagerness!) to test liberal thinking from within the liberal family—is now being squeezed. Internet journalism has made it easy to find opinions that confirm one’s own beliefs and flatter one’s prejudices. Facebook places soothing assurances before our eyeballs. The left and the right are retreating into cocoons of information and opinion, on cable TV and social media.

Accordingly, the New Republic’s fortunes flagged amid the polarization of the Bush years, when its full-throated support for the Iraq war was too much for even many liberal internationalists to bear and when, post-Clinton, liberalism now seemed to need a course correction toward the left, not the center. Though Foer dynamically reinvigorated the magazine, it never regained the wider circulation it once enjoyed.

Wiser ownership could have recognized that although little magazines must adapt to the digital age with strategies for reaching social media users and mobile phone readers, they will never be cash cows. They succeed through influence, not volume. When I worked there in the early 1990s, it was often said that while the magazine had only 100,000 subscribers, it was “the right 100,000”—the political movers who turned to the piercing policy critiques, the intellectuals who engaged with Wieseltier’s unsurpassed “back of the book.”

The impending transformation of the New Republic from a liberal magazine into a “vertically integrated digital media company” is regrettable for many reasons, not all of them sentimental. Conservatives need a liberal magazine that’s unpredictable enough to make them want to read it. Liberals and leftists need a magazine that will prod them to question their beliefs, and revise or strengthen them. All of us need robust intellectual debate of a high caliber that treats politics and ideas with the seriousness that they deserve.