When President Trump finds himself under fire, he turns to Fox News. This past weekend, when the New York Times reported that the FBI had seriously investigated the possibility that the president had been a Russian agent, Trump spoke to his friends at Fox by phone. Host Jeanine Pirro asked sympathetic questions and let the president speak almost uninterrupted, airing his perspective directly to his supporters.

The interview was a stark reminder of just how partisan journalism has become. It’s now the norm. But it’s worth stepping back to remember that this is a recent development, and that the polarization of the media stems in large part from public policy decisions. Such polarization was not inevitable or in any way natural.

In the decades that followed World War II, the big three television networks dominated the news. Together with a few major metropolitan newspapers, they set the tone for the national conversation. On half-hour evening news shows, anchors informed the country as a whole, striving to offer little to no partisan commentary. Sunday morning programs featured interviews with different politicians; occasional specials offered a deep dive on a particular topic. But on virtually all these programs, journalists steered clear of a partisan perspective.

Much of this approach was shaped by the Fairness Doctrine. A policy of the Federal Communications Commission beginning in 1949, the doctrine was based on the notion that the television networks were “public trustees.” Licensed by the federal government, they ought to serve the entire nation, the argument went, by airing competing perspectives on controversial issues. While the policy had been intended to foster a full and fair debate, in practice it led networks to avoid employing anchors or reporters with obvious biases and to play most issues down the middle.

Conservatives never liked the rule. As explained by historian Nicole Hemmer, who is also a co-editor of The Washington Post’s historical analysis section, Made by History, an entire generation of conservatives believed that “objectivity” privileged the liberal establishment because the default views of most broadcasters aligned with those of the Democratic Party. Some local radio hosts flouted the rule by taking aggressively conservative stances on air, only to find the courts forcing their stations to provide equal time to the other side of the debate. When one right-wing radio host in Pennsylvania tried to discredit journalist Fred Crook by describing him as a potential communist, among other things, Crook asked for equal airtime. The Red Lion Broadcast Co. denied the request, but Crook took his case all the way to the Supreme Court and prevailed.

In the landmark Red Lion Broadcasting Co. Inc. v. FCC in 1969, the court ruled that the Fairness Doctrine was constitutional. Free speech, the justices held, was “the right of the viewers and listeners, not the right of the broadcasters.” Therefore, the networks had to provide “ample play for the free and fair competition of opposing views.”

In the 1980s, all of this changed. President Ronald Reagan believed the marketplace, not the government, was the best arbiter for competing viewpoints (and for much else). Notably, Reagan’s appointee for FCC commissioner, Mark Fowler, had long opposed the rule. “We’ve got to look beyond the conventional wisdom that we must somehow regulate this box,” Fowler wrote after the Red Lion ruling. There was nothing special about television’s content and no need for the government to be concerned.

In 1987, the FCC announced that it would no longer enforce the Fairness Doctrine. The commission deemed that the expansion of cable television technology made old arguments about the “scarcity” of airtime irrelevant and that the doctrine inhibited broadcasters from tackling controversial issues. Reagan’s FCC promptly killed it. The Democratic Congress tried to restore the doctrine, but Reagan vetoed the bill.

Almost overnight, the media landscape was transformed. The driving force was talk radio. In 1960, there were only two all-talk radio stations in America; by 1995, there were 1,130. While television news on the old networks and the cable upstart CNN still adhered to the standard of objectivity, radio emerged as a wide-open landscape.

New York’s conservative talk radio icon Bob Grant had long been known for testing the limits of the doctrine, but he now felt freed to engage in outspoken nativism and racism. Discussing the 1991 Los Angeles riot, he called African Americans “screaming savages” and complained that “heaven forbid you talk about white rights.” Immigrants were a favorite target of his, as well. The country, he said, was being flooded with “millions of subhumanoids.”

As Grant played to a local audience, Rush Limbaugh emerged as a national conservative celebrity. With regular attacks on “commie-libs,” “feminazis” and “environmentalist wackos,” Limbaugh quickly cultivated a loyal audience of self-styled “Dittoheads.” Others in the industry took their cues from him. “I’m not sure where the business is going,” Bill O’Reilly told a friend in 1993. “But my gut says it’s going in the direction of Rush, and, man, I’m going to be there.”

The public readily responded to the new model Limbaugh advanced after the demise of the Fairness Doctrine. By 1994, he had an audience of 20 million Americans tuning in on some 650 stations. “What Rush realizes, and what a lot of listeners don’t,” an Atlanta station manager explained, “is that talk-radio programming is entertainment, it is not journalism.”

But if Limbaugh wasn’t exactly journalism, he wasn’t simply entertainment, either. His sway over his audience made him a powerful force on the political right. During the 1992 presidential campaign, President George H.W. Bush courted the radio giant in the hope of winning over his right-wing listeners. In June 1992, the president invited Limbaugh to the White House for an overnight stay in the Lincoln Bedroom. In a telling detail, Bush insisted on carrying Limbaugh’s bag into the White House himself. In exchange for such self-abasement, Limbaugh threw his full support behind the president.

For conservatives, the success of their ideology on talk radio proved that their suspicions about the Fairness Doctrine had been right. Conservative voices had long been ignored in the mainstream media, they claimed, but now that the free market had been unchained, it was clear what the people wanted. By 1995, conservatives accounted for roughly 70 percent of all talk-radio listeners. The end of the Fairness Doctrine had drastically changed the standards of news.

Cable television had never been subject to the Fairness Doctrine, and, indeed, its growth had been a key rationale for ending the policy. But it was transformed by the changes all the same. Seeing the massive audiences that conservative talk radio attracted, cable television entrepreneurs realized that they, too, could thrive by providing the news from a partisan perspective. In 1996, Rupert Murdoch launched Fox News, placing Roger Ailes in charge of the operation. A longtime media consultant for Republicans, Ailes had worked on both of George H.W. Bush’s presidential campaigns and then produced Limbaugh’s television program from 1992 to 1996.

Under Ailes’s direction, Fox News soon embraced a conservative slant, playing up the scandals (and “scandals”) of the Clinton administration. “Talk-radio shows started to go crazy” with coverage of Clinton’s misdeeds, NBC network president Bob Wright remembered. “We were not paying much attention to it at NBC News. And MSNBC wasn’t. CNN wasn’t. And what Fox did was say, ‘Gee, this is a way for us to distinguish ourselves. We’re going to grab this pent-up anger — shouting — that we’re seeing on talk radio and put it onto television.' ”

After 9/11, the network flourished as a full-throated supporter of the war on terrorism. In contrast to its rival CNN, which consciously framed its coverage for a diverse international audience, Fox News increasingly played to conservative viewers at home with nationalistic and populist themes. In January 2002, it finally surpassed CNN in the ratings race.

“Am I slanted and biased?” Fox anchor Neil Cavuto once said in response to critics. “You damn well bet. … You say I wear my biases on my sleeve. Well, better that than pretend you have none, but show them clearly in your work."

Under Trump, the merger of the media giant and modern conservatism has been completed. Several of its hosts serve as informal advisers to the president, while some Fox-affiliated figures, such as former network executive Bill Shine and on-air host Heather Nauert, have taken formal roles in the Trump administration.

Liberals have had their news outlets, too, of course. Late in the Bush presidency, MSNBC became a left-leaning operation, and the liberal “blogosphere” flourished online. But liberals never replicated in scale or scope anything like Fox News or Limbaugh. In the end, none of the liberal outlets formed as cohesive a loyal alliance with the Democratic Party as conservative broadcasters did with the GOP. But their presence only underscores how fractured and fractious the media landscape has become.

And that fracturing and polarization can be traced, in large part, to the end of the Fairness Doctrine.

Though some now seek to revive it, the doctrine is a relic of the past. Today’s communication landscape — including cable, social media and both traditional and satellite TV — is far too unruly for federal officials to regulate. Nor should they try.

But public demand, which conservatives correctly predicted would remake the media a generation ago, can do so again. Polls reveal that the public dislikes the form our media have taken and might be receptive to new models that push back against the partisan tide. If the public demands new models of information, including some that reflect the evenhandedness that ruled during the heyday of the Fairness Doctrine, we may yet see another media revolution.