Matthew Sheffield is the editor of Praxis, an online journal of politics, technology and media.

Donald Trump’s rhetoric draws from old-school “paleolibertarianism.” (David Paul Morris/Bloomberg)

Hillary Clinton and her campaign have been going out of their way to make a surprising argument about Donald Trump: He’s not really a Republican.

At the Democratic convention, several speakers said Trump represented a complete break from the conservative traditions of the GOP. Last month, Clinton delivered a similar message in a speech linking Trump to the white-nationalist political movement known as the “alt-right.” “This is not conservatism as we have known it,” she asserted.

According to Clinton — and many conservative intellectuals who oppose Trump — the conspiratorial, winking-at-racists campaign he has been running represents a novel departure from Republican politics.

The alternative right has come under fire from Hillary Clinton and establishment Republicans, but it has been seeping into American politics for years as a far-right option for conservatives. Here's what you need to know about the alt-right movement. (Jenny Starrs/The Washington Post)

That’s not quite true, though. Trump’s style and positions — endorsing and consorting with 9/11 truthers, promoting online racists, using fake statistics — draw on a now-obscure political strategy called “paleolibertarianism,” which was once quite popular among some Republicans, especially former presidential candidate Ron Paul.

Formally, Sen. Rand Paul (R-Ky.) may be his father’s political heir. But there’s no question that the paranoid and semi-racialist mien frequently favored by Trump originates in the fevered swamps that the elder Paul dwelled in for decades. Most people who back Trump don’t do so for racist reasons, but it’s incredible how many of the same white nationalists and conspiracy theorists to whom Ron Paul once catered are now ardent Trump supporters. It’s because Trump and Paul speak the same language.

Mainstream libertarians have been agonizing over this legacy among themselves for some time, hoping that either the elder or younger Paul would definitively denounce the movement’s racialist past, but no such speech has ever come. Instead, the paleolibertarian strategy concocted decades ago as a way to push for minimal government threatens to replace right-wing libertarianism with white nationalism.

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The figure whose ideas unify Pauline libertarians and today’s Trumpists is the late Murray Rothbard, an economist who co-founded the Cato Institute and is widely regarded as the creator of libertarianism.

Nowadays, many libertarians like to portray their ideology as one that somehow transcends the left-right divide, but to Rothbard, this was nonsense. Libertarianism, he argued, was nothing more than a restatement of the beliefs of the “Old Right,” which resolutely opposed the New Deal and any sort of foreign intervention in the early 20th century. Many of its adherents, such as essayist H.L. Mencken, espoused racist viewpoints, as well.

As moderate Republicans such as Dwight Eisenhower and “New Right” Christian conservatives such as William F. Buckley became more influential within the Republican Party in the 1950s and ’60s, the future creators of libertarianism gravitated instead toward the work of secular anti-communist thinkers such as economist Ludwig von Mises and novelist Ayn Rand.

There had always been some sympathy for racism and anti-Semitism among libertarians — the movement’s house magazine, Reason, dedicated an entire issue in 1976 to “historical revisionism,” including Holocaust revisionism. It also repeatedly ran articles in defense of South Africa’s then-segregationist government (though by 2016, the magazine was running articles like “Donald Trump Enables Racism”). But it was Rothbard’s founding of the Ludwig von Mises Institute in 1982 that enabled the fledgling political movement to establish affinity with the neo-Confederate Lost Cause movement.

Almost immediately after its creation, the Mises Institute (headquartered in Auburn, Ala.) began publishing criticism of “compulsory integration,” attacks on Abraham Lincoln and apologia for Confederate leaders. Institute scholars have also spoken to racist groups such as the League of the South. Rothbard even published a chapter in his book “The Ethics of Liberty” in which he said that “the purely free society will have a flourishing free market in children,” although he didn’t specify the races of the children who might be sold.

These and many other controversial views advocated by Mises writers make sense from a fanatical libertarian viewpoint. But they also originate in a political calculation Rothbard revealed in a 1992 essay lamenting the defeat of Republican white nationalist and former Ku Klux Klan leader David Duke in the 1991 Louisiana governor’s race by a bipartisan coalition.

Expanding on themes raised two years earlier by his longtime partner and friend Llewellyn “Lew” Rockwell, an editor and fundraiser for libertarian causes, Rothbard argued that Duke’s candidacy was vitally important because it made clear that the “old America” had been overthrown by “an updated, twentieth-century coalition of Throne and Altar” and its “State Church” of government officials, journalists and social scientists.

Besides commending Duke as an exemplar of the kind of candidate he was looking to support, Rothbard also invoked the “exciting” former senator Joe McCarthy of Wisconsin — not because of his economic views but because he was a brash populist prone to doing erratic things. Rothbard’s description of McCarthy seems eerily similar to the campaign that Trump has been running:

“The fascinating, the exciting, thing about Joe McCarthy was precisely his ‘means’ — his right-wing populism: his willingness and ability to reach out, to short-circuit the power elite: liberals, centrists, the media, the intellectuals, the Pentagon, Rockefeller Republicans, and reach out and whip up the masses directly. . . . With Joe McCarthy there was a sense of dynamism, of fearlessness, and of open-endedness, as if, whom would he subpoena next?”

To solve the problem that few Americans are interested in small government, Rothbard argued that libertarians needed to align themselves with people they might not like much in order to expand their numbers. “Outreach to the Rednecks” was needed to make common cause with far-right Christian conservatives who hated the federal government, disliked drugs and wanted to crack down on crime.

All of these paleolibertarian positions were offered in Duke’s 1990 Senate campaign and 1991 gubernatorial campaign. But they were also offered by another politician Rothbard admired: Ron Paul, the Libertarian Party’s presidential candidate in 1988.

Rothbard and Paul had known and worked with each other in the 1970s, when they came to know Rockwell. Rockwell would work closely with both men, serving as Paul’s congressional chief of staff until he left to found the Mises Institute with Rothbard.

Rockwell also was the editor of a series of printed newsletters for both men in the ensuing decades. Paul’s publications became famous during his Republican presidential campaigns. Their controversial nature is no surprise, given that Paul had coyly endorsed the paleolibertarian strategyshortly after it was devised.

Sold under various titles, the highly lucrative newsletters frequently stoked racial fears, similar to what Trump has been doing this year, though they went further — one even gave advice on using an unregistered gun to shoot “urban youth.” Another issue mocked black Americans by proposing alternative names for New York City such as “Zooville” and “Rapetown,” while urging black political demonstrators to hold their protests “at a food stamp bureau or a crack house.”

The publications also repeatedly promoted the work of Jared Taylor, a white nationalist writer and editor who is today one of Trump’s most prominent alt-right backers. Articles also featured anti-Semitic conspiracy theories and frequent rants against gay men.

Paul later said he didn’t write the newsletters. But regardless of their authorship, the image they created made him attractive to white nationalists. Those supporters weren’t numerous enough to get Paul the GOP presidential nomination, however, and paleolibertarianism began fizzling out.

In the past few years, however, it’s been reborn as the alt-right, as a new generation of libertarians discovered their hidden heritage and began embracing racism and conspiracy theories. Many alt-right writers trace their roots to Rothbard. As one of them, Gregory Hood, put it, paleolibertarian theories about race and democracy “helped lead to the emergence [of the] Alternative Right.” Rothbard’s call for “sovereign nations based on race and ethnicity” is very similar to beliefs Trump’s alt-right supporters express today.

In 2016, many, if not most, of the extremists who formerly supported Paul have rallied to Trump’s side. In 2007, Paul won an endorsement and a $500 campaign contribution from Don Black, the owner of Stormfront, a self-described “white pride” Web forum. Despite a torrent of criticism, Paul refused to return the money. This March, Black encouraged his radio listeners to vote for Trump, even if he wasn’t perfect.

Memphis-based white nationalist radio host James Edwards supported Paul and likewise backs Trump. His reputation didn’t dissuade either candidate from associating with him. In July, Edwards attended the Republican National Convention on a press pass even after the Trump operation was subjected to embarrasing media coverage for allowing Edwards to interview Donald Trump Jr. For his part, Paul agreed to appear on Edwards’s program in 2006 but canceled at the last minute.

Duke, who is again running for Senate, has also repeatedly expressed his admiration of both men. While Trump has mostly disavowed Duke, Paul said in one of his newsletters that Duke’s political views were “just plain good sense,” despite the “baggage” of his former Klan involvement.

After Rand Paul came to the Senate in 2011, and as he eventually began planning his own presidential campaign, there was some speculation that conservatives might be entering a “libertarian moment.” Things didn’t turn out that way. Instead, the American right seems to have entered a paleolibertarian moment.

CORRECTION: An earlier version of this story incorrectly described Reason’s 1976 special issue on revisionism and its coverage of apartheid South Africa. The February 1976 issue included an article that discussed Holocaust revisionism, but it was not entirely dedicated to the subject. Also, while the magazine did run several articles defending apartheid, it did not editorialize in favor of the system.