In recent weeks, Sen. Bernie Sanders has criticized his rivals for the Democratic presidential nomination for having too much “baggage” to win the diverse coalition needed to defeat President Donald Trump in November. But as the Vermont independent tops national polls for the first time, newly unearthed baggage from his own decades-long political career could call his own past statements and judgment into question.

As the leading member of a self-described “radical political party” in the 1970s, Sanders repeatedly compared Vermont workers to enslaved black people, according to archival interviews obtained by The Daily Beast. In one 1976 conversation, Sanders told a local newspaper that the sale of a privately held mining company by its founders harkened back to “the days of slavery, when black people were sold to different owners without their consent,” and compared the service economy to chattel slavery.

“Basically, today, Vermont workers remain slaves in many, many ways,” Sanders said in another interview in 1977, in which he compared the burgeoning service industry in the nearly all-white state to the enslavement of black Americans at the nation’s founding. “The problem comes when we end up with an entire state of people trained to wait on other people.”

At the time, Sanders was the chairman of the Liberty Union Party, a Vermont offshoot of the socialist People’s Party. The future senator and presidential hopeful had run for statewide office as the party’s nominee four times—once for the U.S. Senate in 1972, and once for governor in 1976, when he garnered 6 percent of the vote. Those bids were unsuccessful, but the message in the interviews was not dissimilar from that of his 2020 presidential campaign, with an emphasis on working-class solidarity and the disruption of a corrupt political elite enabled, he said in the 1976 article, by “a handful of billionaires [who control] the economic and political life of the nation.”

“Your average person is thoroughly disgusted and turned off to the political and economic structure as it now exists in America,” Sanders told the Rutland Daily Herald on Oct. 8, 1976, “but has been led to believe that there is no alternative or that the only alternative is a political system like the Soviet Union’s.”

But Sanders’ previously unreported comparisons between the conditions of Vermont workers and that of enslaved people evoke a different element of his campaign—assertions by critics that he tends to view systemic racism primarily through the lens of economic disenfranchisement.

“The racial wealth gap lingers in part because the politicians who could close it are funded by the very corporate donors who continue to benefit from it,” Sanders wrote in an illustrative op-ed in The Washington Post in July 2019. “As long as corporations can rely on the indifference to black lives as a cover for their exploitation, they will continue to do so.”

In the first interview, published in October 1976 when Sanders was the Liberty Union Party’s nominee for governor, the future senator responded to the announced sale of the century-old Vermont Marble Company to a Swiss conglomerate by calling for worker control of businesses, calling it “absolutely absurd” that the family that owned Vermont Marble could have “the unilateral right” to sell the company without the approval of its employees.

“We believe ultimately that companies like Vermont Marble should be owned by the workers themselves and that workers—not a handful of owners—should be determining policy,” Sanders said. “If a worker at Vermont Marble has no say about who owns the company he works for and that major changes can take place without his knowledge and consent, how far have we really advanced from the days of slavery, when black people were sold to different owners without their consent?”

The population of Vermont was, at the time, more than 99 percent white and roughly 0.2 percent black.

Later in the 1976 article, Sanders called for “the working people of this country, who constitute the vast majority of the population,” to seize control of the economy to thwart poor labor conditions, “if we are free people and not slaves.”

In the second interview, conducted on the occasion of Labor Day in 1977, Sanders—then the Liberty Union Party’s chairman—said that the decline of industry and the increase in service-sector jobs meant that “basically, today, Vermont workers remain slaves in many, many ways.”

“How can a worker be happy with his or her job when he or she has no control over that job?” Sanders asked. “The problem comes when we end up with an entire state of people trained to wait on other people.”

In that interview, Sanders pointed to a worker-owned asbestos plant in Lowell, Vermont, as an example of the kind of worker-owned enterprise that he envisioned in the economy of the future.

“In the long run,” Sanders said, “what we are talking about is a peaceful revolution.”

A Sanders campaign official told The Daily Beast that as a member of the Senate Committee on Health, Education, Labor, and Pensions, Sanders has long been an opponent of modern-day slavery in the context of poor work conditions, and has been involved in investigating such cases as a senator.

Sanders, the official noted, has also called for the United States to officially apologize for slavery.

Although Sanders has stated that the United States was founded on “racist principles” and has called for an end to “physical, political, legal, economic, and environmental” violence against Americans of color, the Vermont senator has been on the receiving end of criticism by those who see his description of economic inequality and institutional racism as “parallel problems” as a way to subsume the cultural underpinnings of racism into a class-based paradigm.

In an interview with The New York Times’ editorial board released last week, Sanders said that the political appeal of racism is rooted in economic and political disenfranchisement—an “economic anxiety” explanation for Trump’s rise that some critics see as dodging the heart of the issue.

“I criticized both Warren and Sanders back in 2017 for trying to make Trump’s appeal to racism all about economics and poverty. It’s just not true. But Bernie’s still saying it,” tweeted Intercept columnist Mehdi Hasan, who has written about the issue in the past. “I get why, he’s just wrong, sadly.”

Despite a long history of advocating for civil rights, Sanders faced difficulty in the 2016 Democratic presidential primary winning over voters of color, particularly across the Deep South, which contributed to his loss to former Secretary of State Hillary Clinton. In South Carolina, where black voters account for two-thirds of the Democratic primary electorate, Clinton defeated Sanders by nearly 50 percent, winning African-American voters by a 72-point margin. Current polling indicates that Sanders’ support among black voters is healthier than it once was, particularly among those under 50, but he still trails former Vice President Joe Biden by more than 20 points.

The slavery comments also threaten to undercut one of Sanders’ main selling points as a candidate: his consistency. Supporters of the Vermont senator often note that fellow progressive candidate Sen. Elizabeth Warren of Massachusetts was once a registered Republican, and Biden’s past support for the invasion of Iraq has put him on the defensive in recent weeks as Sanders has victory-lapped his vote against the war. Sanders, as evinced by the interviews with the Herald, has been a champion of fighting income and wealth inequality since before some of his Democratic rivals were even born.

“I categorically disagree with the idea that the only alternatives facing the people of America and Vermont are, on the one hand, a system in which a handful of billionaires controls the economic and political life of the nation,” Sanders said in the 1976 interview, “or, on the other hand, a situation in which the political hacks sitting at the head of the state bureaucracy and the military and the secret police control the economic political life of their countries.”

Although Sanders has avoided personally hitting his opponents, leaving that work instead to his surrogates and supporters, his campaign has declared that questions about past decisions and statements by Democratic rivals are fair game.

“Before folks attempt to frame an accurate critique of a candidate’s record as an ‘attack,’ I hope they consider whether doing so helps the millions of voters who need to hear the underlying facts of a candidate’s record/policies to make an informed decision about their futures,” tweeted Briahna Joy Gray, the Sanders campaign’s national press secretary, on Wednesday.