John Tanton, who over 40 years almost single-handedly built the American anti-immigration movement around a core of rancid white nationalism, is dead. He was 85, and he left a legacy of racist opposition to immigration that, among other things, has been fully embraced by the president of the United States.

Tanton died earlier this week in his home town of Petoskey, Michigan, after a long battle with Parkinson’s disease. He was mourned by colleagues in the many nativist groups he founded, one of whom described the one-time ophthalmologist as a “Renaissance man” who had been unfairly tarred by his critics.

Most people familiar with Tanton’s work didn’t see it that way.

After a series of internal memos leaked, and especially after the Southern Poverty Law Center unearthed a trove of his personal papers in a university library, the real Tanton was revealed. He was a man who warned privately of a “Latin onslaught,” corresponded regularly with leading racist thinkers, Holocaust deniers and anti-Semites, and insisted that “for European-American society to persist requires a European-American majority, and a clear one at that.”

In 1979, Tanton founded the Federation for American Immigration Reform (FAIR), still the country’s most important nativist organization. In subsequent years, he formed the Center for Immigration Studies, NumbersUSA, and a slew of other groups. His U.S. Inc. organization funded many others. While some groups camouflaged their racial attitudes more or less successfully, almost all of them were infected with the basic idea that America was a white man’s country.

By the 1990s, that camouflage was wearing thin. One example: In 1994, the Social Contract Press, the publishing arm of Tanton’s empire, republished an English translation of the savagely racist French novel The Camp of the Saints, which Tanton once described as his favorite book. The book that Tanton called “prescient” describes the invasion of France by “swarthy hordes” of Indians, “grotesque little beggars from the streets of Calcutta,” who arrive in a desperate refugee flotilla. It is particularly critical of white liberals, who, rather than bar the immigrants, “empty out all our hospital beds so that cholera-ridden and leprous wretches could sprawl between white sheets… and cram our nurseries full of monster children.”

Tanton wrote that we are “indebted” to author Jean Raspail, “for his insights into the human condition, and for being so many years ahead of his time. History will judge him more kindly than have some of his contemporaries.” Tanton’s edition of the book carried a special afterword from Raspail, who told his readers that “the proliferation of other races dooms our race, my race, to extinction.”

It wasn’t always so with Tanton. In the 1960s, he and his wife founded a chapter of Planned Parenthood in Michigan. A few years later, he became a leader of the Sierra Club and he remained an environmentalist throughout his life. He was, in the vernacular of the time, a liberal.

But even then, he was already developing an admiration for eugenics—the utterly discredited “science,” favored by the Nazis, of creating a better human race through selective breeding. As early as 1969, Tanton wrote officials in Michigan asking if state law allowed forced sterilization. He was concerned, he wrote, about “a local pair of sisters who have nine illegitimate children between them.”

Almost 30 years later, he was still mulling the same questions.

“Do we leave it to individuals to decide that they are the intelligent ones who should have more kids?” he wrote to eugenicist Robert K. Graham. “And more troublesome, what about the less intelligent, who logically should have less? Who is going to break the bad news, and how will it be implemented?”

In many ways, what Tanton sought above all was to overturn the 1965 Immigration Act that ended a racist quota system that had been in place since 1924. He idolized John Trevor Sr., a key architect of that quota system, which mostly limited immigration to northern and northwestern Europeans.

Trevor was no moderate. He distributed pro-Nazi propaganda, drew up plans to crush uprisings of “Jewish subversives,” and warned of “diabolical Jewish control” of America. Tanton, however, wrote a FAIR board member in 2001 that Trevor’s work should serve as “a guidepost to what we must follow again this time.”

When President Lyndon Johnson signed the 1965 act, he celebrated the demise of Trevor’s legislation, saying “that it will never again shadow the gate to the American nation with the twin barriers of prejudice and privilege.”

In the early 1990s, Tanton’s white nationalist views were again on display, this time in a proposal he made to a FAIR board member. He wanted to create a group called League for European American Defense, Education, and Research. He came up with the idea after talking to white nationalists including Jared Taylor, who has written that black people are incapable of sustaining civilization.

A few years later, he complained to a Detroit Free Press reporter that unless the borders were closed, the United States would be overrun by immigrants “defecating and creating garbage and looking for jobs.”

Tanton did not take kindly to criticism. I know this because, as an official of the Southern Poverty Law Center, I was among those frequently attacked by him. A special 2010 issue of the Social Contract Press, of which Tanton was then publisher, was dedicated to slamming the Center’s “Profiteers of Hate,” featuring a cover cartoon of me and two colleagues, witch-like, stirring a cauldron of “slime.”

Inside the 84-page special edition, one article compares me to Vladimir Lenin: “Perhaps Mr. Potok knows something of that Soviet leader. He once did a congenial interview with the Socialist Workers Party, which, on its website, endorses the goals of Marx and Lenin.”

Perhaps the most remarkable thing about Tanton and the movement he built is the level of prominence his organizations achieved despite their ideology. His groups were largely responsible for killing comprehensive immigration reform in 2007. FAIR has testified more than 100 times before Congress. And several key officials from Tanton’s groups have now joined the Trump administration.

John Tanton can’t be blamed for President Trump’s racist attack this week on four Democratic congresswomen of color, who he said should “go back” to the countries they “originally came from… whose governments are a complete and total catastrophe.” (All four are citizens, and three were born in the U.S.)

But he did an enormous amount to legitimize the kind of racist attacks the president and many other politicians today engage in regularly. After all, Tanton’s views were pretty plain if you looked. “Demography is destiny,” he wrote once. “We decline to bequeath to our children minority status in their own land.”

That, in a phrase, is the essence of modern white nationalism.