Robert F. Kennedy Jr. is a man of many misguided ideas. He thinks that vaccinations are harmful, that Wi-Fi radiation causes cancer, and that chemicals in the water supply are producing gender dysphoria. Most political commentators do not share these ideas, but they have implicitly adopted another of the presidential hopeful’s questionable notions: that Kennedy’s voters care about Kennedy’s ideas and are supporting him because of them.

“RFK Jr. says things—whether about vaccines causing autism, SSRIs leading to school shootings, or the CIA killing his dad and uncle—that are described by mainstream media as disinformation and ideas that are simply beyond the pale,” the political commentator Bari Weiss wrote. “But his high polling suggests that many Americans are tuning in to what he has to say. And perhaps they think that we have drawn the lines of debate too narrowly.”

Other analysts have adopted this reading in making the case for experts to publicly debate Kennedy and his proposed policies. “If a large chunk of the public is in the grip of mistaken ideas about these issues, part of the job of experts is to wade in and correct those ideas,” the leftist writer Ben Burgis argued. “If you don’t think he should be publicly debated, you need some other theory of how the curious can be persuaded away from his ideas,” the conservative New York Times columnist Ross Douthat wrote.

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All of these arguments assume that Kennedy is polling in double digits because his personal positions are resonating with the electorate. But this is a mistake. Although some voters do share Kennedy’s skepticism of the COVID-19 vaccines, they are predominantly Republicans; few Americans of either party oppose all childhood vaccinations, as he does. In reality, Kennedy’s popularity comes not from his odd ideas, but from his anti-establishment affect. He has not unearthed a new constituency for banning wireless internet and immunizations; he has tapped into a very old one that fundamentally repudiates the American political system and its official options. Kennedy’s campaign is a protest movement, not an intellectual argument, and seeking to rebut his specific stances misunderstands his appeal and dignifies his fringe fantasies with respect they do not command among voters.

Presidential-primary polling this century tells a clear story: About a quarter of voters reject their party’s political establishment and resent its attempts to anoint a presidential nominee. These voters want no part of a coronation, whether the chosen candidate is Hillary Clinton or Jeb Bush, and when the opportunity presents itself, they readily rally behind other contenders who echo their anger at the political class. For decades, this bloc has boosted candidates of deeply divergent backgrounds who share little in common besides their anti-establishment outlook.

In 2004, the beneficiary of this energy was former Vermont Governor Howard Dean, whose campaign declared that he was running against the Democratic “establishment” and regularly denounced the “Washington Democrats in power.” In the early primary races, Dean garnered around a fifth of votes, but he ultimately flamed out, unable to expand beyond this showing. In 2008, first-term Senator Barack Obama captured the same constituency with his pointed critique of the Iraq War, which doubled as a critique of those who had supported the ill-fated military action—not just Clinton, Obama’s primary opponent, but many others among his party’s elites. By combining this insurgent support with a commanding majority of Black voters, Obama was able to dethrone the front-runner and nab the nomination.

In 2016, as Obama was departing the scene, another Vermont politician picked up the anti-establishment torch. In his own words, Senator Bernie Sanders was not merely a progressive calling for reform but a “socialist” calling for “revolution.” In interviews and public appearances, he attacked the Democratic Party, even as he sought to lead it. And he repeatedly assailed the “corporate media,” by which he meant not simply conservative channels such as Fox News but also mainstream outlets including CNN, ABC, and NBC. If this rhetoric sounds familiar, it should—and not just when it comes from Kennedy’s campaign. After all, on the other side of the aisle, another candidate rode similar sentiment to victory against a divided GOP field.

Few remember today, but the slate of candidates for the 2016 Republican presidential primary was reputed to be one of the strongest in recent memory, brimming with electorally successful Republican politicians including Jeb Bush, Chris Christie, Scott Walker, and Marco Rubio. On paper, these men represented their party’s best and brightest. Then Donald Trump crashed that party. He dismissed Bush as a low-energy establishment lackey, mocked past presidential nominee John McCain for being captured during the Vietnam War, and brushed off a public denunciation from the party’s prior standard-bearer, Mitt Romney.

That Trump had previously explored running for president as a third-party candidate and once told CNN, “In many cases, I probably identify more as a Democrat” did not hinder his campaign. If anything, it burnished his outsider credentials, much as Sanders’s previous registration as an independent had bolstered his insurgent bona fides, and Kennedy’s famous last name now grants him credibility as a critic of his class. Again and again, Trump told his supporters that he was being persecuted on their behalf, and that those in power did not want anyone to hear what he had to say.

The point here is not that Trump, Sanders, Obama, and Dean propounded similar positions or worldviews. They obviously did not. But each of them played the same symbolic role for primary voters: as protest candidates against an ossified and corrupt elite. Their personal affect, rather than their policy aspirations, was a key source of their electoral appeal. And the same is true for Kennedy today.

The notion that some voters choose their candidates based on vibes rather than a careful examination of their specific stances is anathema to many pundits and professional politicians, who invest a tremendous amount of time in parsing such positions. But the historical record is clear. Just listen to Kennedy himself.

In an interview with Weiss, Kennedy noted that his slain father “was also a populist leader” who challenged a sitting Democratic president. He then offered a telling anecdote about what this meant. Kennedy recalled how he’d accompanied his father’s body by train from New York to Washington, D.C., after his assassination, and was met on the tracks by thousands of supporters—Black Americans in cities such as Trenton and Baltimore, and white Americans in the countryside. “There were hippies, there were people in uniform, there were Boy Scouts,” Kennedy recounted. “Many people, white men and women, holding signs that said Goodbye, Bobby, holding American flags, holding up children.”

But four years later, the younger Kennedy had a rude awakening about these same people. Examining demographic data from the 1972 presidential campaign, he discovered that “the predominant numbers of white people” who had supported his father had not voted for George McGovern, “who was aligned with my father on almost every issue,” but rather “ended up supporting George Wallace, who was antithetical to my father in every way—he was a fierce, rampant segregationist and racist.”

In the interview, Kennedy casts this about-face as an illustration of how populist energy can be channeled for good or ill. But he can’t quite bring himself to acknowledge the obvious implication: For backers of Kennedy Sr., as for those of Kennedy Jr., the choice was never about policies but about a posture, which is why the same voters were willing to support outsider candidates with seemingly opposite ideals.

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This is a consistent pattern. At the 2016 Democratic national convention, two prominent Sanders supporters officially put forward his candidacy for the nomination: then-Representative Tulsi Gabbard and former Ohio State Senator Nina Turner. The two women could not have been more different. Gabbard went on to become a right-wing critic of the Democratic Party, and now serves as a commentator on Fox News. Turner, by contrast, is a socialist firebrand who has repeatedly challenged the Democrats from the left. And yet, both supported Sanders against Clinton in 2016; today, Gabbard is defending Kennedy on Fox News and Turner is demanding that Biden debate him. Persona over policy, affect over aspiration.

What does all of this mean for Kennedy’s presidential prospects? In most cases, an anti-establishment approach puts a ceiling on a politician’s appeal. In a democracy, the establishment is the establishment for a reason: It retains power because most voters like what it is selling. For this reason, running against the party you seek to lead is generally a recipe for frustration, as Sanders discovered, first with Hillary Clinton and then with Joe Biden. It’s hard to beat a defined establishment alternative when your base is capped at roughly a quarter of the primary electorate.

But an anti-establishment insurgent can win when a clear alternative doesn’t exist, which is how Trump managed to succeed in 2016. Facing a divided primary field filled with candidates more interested in attacking one another than him, Trump rode his minority faction to victory, executing a hostile takeover of the Republican Party in the process. Unfortunately for Kennedy, he faces a clear establishment favorite in the incumbent president. Having consolidated the anti-establishment vote, the eccentric activist has nowhere else to go, and unlike Obama in 2008, he has no other natural constituency. As the Semafor reporter David Weigel recently noted, “When [Kennedy] entered the race, public polling put his support in the teens. Two months later, after copious earned media, those numbers haven’t budged, and the share of primary voters who say they won’t vote for him is rising.”

Populist insurgents like Kennedy point to their polling as evidence of the popularity of their ideas. But in actuality, those numbers reflect the real but limited popularity of their anti-establishment posture. In American politics, there is always a market for someone calling to burn down the entire edifice; the specific kindling is beside the point.