On Monday, Sen. Lindsey Graham went on Fox & Friends and called the “Squad”—the four freshmen representatives and women of color currently being targeted by President Donald Trump—“a bunch of communists.” The language sounded familiar to some. “Since at least the 1950s,” activist Bree Newsome Bass said on Twitter, “ ‘communist’ has become a popular coded word for n—-r. Let’s be real.” On Wednesday, “Squad” member Alexandria Ocasio-Cortez added her own explanation: The term communist “was one of the preferred smears against integrating schools, & one of the main attacks segregationists used against MLK Jr.” But this redbaiting sideshow to the escalating racist rhetoric from the White House has even deeper roots than that. “Black activists are Reds” is, in fact, one of American racism’s greatest hits.

A hundred years ago, during the so-called Red Summer of 1919—a term coined by writer James Weldon Johnson, then field secretary for the NAACP—social conflict between blacks and whites turned violent in Chicago, D.C. (where riots broke out on July 19), Arkansas, and many other places. As I wrote for Slate a few years ago, “Red Summer” marked a new determination among black people to fight back against the aggression that white neighbors brought to their doors. Demobilized black veterans, who symbolized black advancement, were often direct targets of white violence; they also helped their communities fight back against it. Cheering on this new spirit, writers and journalists published jubilant exhortations in the black press. Poet Claude McKay’s sonnet “If We Must Die,” which ran in the socialist magazine the Liberator, called in stirring terms for resistance: “Like men we’ll face the murderous, cowardly pack,/ Pressed to the wall, dying, but fighting back!”

The Red Summer was also the beginning of another tradition: the surveillance and redbaiting of black activists—or, really, just any black person who wanted social change. During and right after World War I, wrote historian Theodore Kornweibel Jr. in his book Seeing Red: Federal Campaigns Against Black Militancy, 1919-1925, “any African Americans who spoke out forcefully for the race—editors, union organizers, civil rights advocates, radical political activists, and Pan-Africanists—were likely to be investigated by a network of federal intelligence agencies.” Whether or not these activists were actually sympathetic to socialism, communism, anarchism, or Bolshevism, their government was extremely convinced that they were. Whenever violence occurred during the Red Summer—especially in the instances when black people resisted that violence—investigators directed by then–24-year-old Justice Department official J. Edgar Hoover fanned out to interview participants and find out how they had been radicalized. Although his agents in the field didn’t often uncover evidence of such radicalization, Hoover asked them to try, again and again.

The linkage of even the slightest hint of black activism with “un-Americanism” began with American involvement in the war, in 1917. Wartime paranoia fed the growth of new government surveillance and intelligence agencies, often aimed at surveilling dissidents and critics of the American government. As historian Kenneth O’Reilly put it in a review of Kornweibel’s book, the nascent federal intelligence agencies “shared an … eminently simple assumption … that ‘second-class’ citizens would have second-class loyalties.” Reports in the white press hyped the idea that Germans were spreading pacifist propaganda among Southern black communities, inciting opposition to the war effort. Federal investigative agencies, historian Mark Ellis writes in his book Race, War, and Surveillance: African Americans and the United States Government During World War I, thought that any resistance to the abuses of Jim Crow might be evidence of German meddling.

Hoover seems to have been unable to grok the idea that black people would ever rise up without the help of “foreign” agitators.

After the war, the surveillance of black activism continued. Agencies, Kornweibel wrote, “skipped nary a beat in making a transition from dread of German subversion and radicals to the Red Scare.” The “First Red Scare”—often forgotten, while ’50s-era McCarthyism has dominated our historical memory—began when anarchists led by journalist and radical Luigi Galleani sent dozens of bombs to the homes of politicians, officials, businessmen, and journalists in April 1919. The event touched off a series of government reactions and culminated in the “Palmer Raids” of November 1919 and January 1920. These were ordered by Attorney General Mitchell A. Palmer, and they targeted Italian and Eastern European immigrants, Communists, anarchists, and labor activists; about 4,000 were arrested, and 800 were deported.

Many government officials couldn’t believe that the close timing of the Galleanist bombings and the nationwide upswing in black resistance to white violence during the Red Summer could be a coincidence. J. Edgar Hoover was among them. Hoover was head of the Justice Department’s Bureau of Investigation’s General Intelligence Division at the time. (He rose to become the director of the Bureau of Investigation in 1924, and the “BI” gained a “Federal” and became the “FBI” in 1935.) In his article about Hoover’s quixotic fixation on the connection between black radicalism and “Bolshevism” that summer, Mark Ellis chronicles the many times Hoover tried, and failed, to find evidence of this nexus. This story of fixation would almost be funny, if it weren’t so chilling.

After the Washington riots, Ellis writes, the reports of Hoover’s agents on the ground show that they were “plainly under orders to show what part had been played by subversive propaganda among blacks.” In their written reports, they “presented the resolve of blacks as extraordinary and significant—as if for whites to band together to harm blacks was natural, and for blacks to retaliate was not.” At the same time, the agents found no evidence of connections between the riot and “radical or Bolshevik propaganda.” In Chicago, after the violence there, the agents likewise found no evidence that the riots were connected to any of the main radical boogeymen, and eventually closed the investigation.

Even so, Hoover continued to emphasize to his agents in Chicago and Washington that he wanted to know more about the relationship between radicalism and the riots, asking the Chicago office in August to investigate the finances of black newspapers to see whether “the I.W.W. [Industrial Workers of the World] organization or other radical elements” were opening their pocketbooks to the publications. Hoover called for investigation into “radical activity” again after a race riot in Omaha, Nebraska, on Sept. 28, 1919, but “none could be found,” Ellis writes. After white vigilantes and federal troops killed 100 to 200 black people in Phillips County, Arkansas, on Sept. 30, investigators found no evidence that the IWW had been involved in encouraging the local black sharecroppers’ union to resist landowners’ exploitation.

Despite this lack of evidence, Hoover found ways to make sure that this idea of the connection between black resistance and “communism” got out into public consciousness. At the end of July 1919, an article in the New York Times on the recent unrest included a quote from an anonymous “federal official” that (Ellis believes) must have come from either Hoover himself or another official, Roger Adger Bowen, who would not have spoken without Hoover’s approval. This unnamed source told the Times that the government had reason to believe that “negroes of this country are the object of a vicious and apparently well financed propaganda,” stemming from the I.W.W., “certain factions of the radical Socialist elements and Bolsheviki.”

Once in the white press, the unsubstantiated idea moved into the realm of politics. Ellis writes that on Aug. 25, Rep. James F. Byrnes of South Carolina “commandeered a congressional debate on education” to argue for the conspiracy theory that radicalism must be at the root of the riots. “When sanguinary conflicts take place in cities so widely separated and within so short a time, the cause is general and not local,” Byrnes contended. He cited the New York Times report, and said the southern black man “is happy and contented and will remain so if the propagandist of the I.W.W., the Bolsheviki of Russia, and the misguided theorist of other sections of this country will let him alone.”

In the fall of 1919, the Department of Justice submitted a special report to Congress on its recent “investigation activities,” warning of a “wave of radicalism” that seemed to have “swept across the country.” The report marshaled its argument that the Red Summer riots had been caused by radicalism; this argument was all from “common sense,” not from evidence. “The ill-governed [read: resistant] reaction toward race rioting; the threat of retaliatory measures in connection with lynching; the more openly expressed demand for social equality” were all cited as reasons why the two social phenomena must have been connected. Kornweibel notes that it seems to have particularly bothered the author of this report that publications in the black press voiced “pride in fighting back against white rioters.” This, Ellis writes, “is a model Red Scare analysis of the race problem, with its presumption that retaliating against violence, demanding equality, and disagreeing with [President] Wilson were not simply deplorable, but proof that blacks were embracing Bolshevism.”

Hoover’s later fixation on the possible “communist” backers of Martin Luther King Jr. and other civil rights leaders has to be seen as a continuation of his early efforts to link black resistance to radicalization. The Red Summer, Ellis writes, “made such a deep and lasting impression on Hoover that he retained throughout his long working life the views he formed about black activists at the age of 24.” Ellis notes that as early as 1956, Hoover was “privately warning Eisenhower’s cabinet” that the civil rights movement was “vulnerable to infiltration.” FBI agents investigating the riots of the 1960s were asked to find out whether they were instigated by “subversive or radical groups”—despite Hoover’s public endorsement of the Johnson administration’s position to the contrary. By 1964, he had resurrected this theme completely, and was publicly denouncing the “Communist influence” within the “Negro movement.”

Whenever I’m looking at a genealogy of a particular strain of American racism, I try to understand not only how old it is, but why it’s so durable. This 1919 flare-up of the “black people who ask for more must be Communists” trope has roots in white people’s complete and total belief in a supposedly “natural” racial hierarchy. Hoover seems to have been unable to grok the idea that black people would ever rise up and resist without the help of “foreign” agitators—and, as Rep. Byrnes’ speech shows, Hoover certainly wasn’t alone.

But the association between blackness and “socialism” goes back even further than this. As historian Heather Cox Richardson pointed out on Twitter, you can see the public association between black Americans and “socialist” or “communist” ideas begin as early as Reconstruction. Richardson’s book The Death of Reconstruction: Race, Labor, and Politics in the Post-Civil War North, 1865-1901, shows how Northerners who were initially supportive of freedpeople right after the war came to turn against those who asked for help and protection from the federal government, as they tried to make a place for themselves and earn a living among hostile ex-Confederate neighbors. The idea that they deserved this protection, Richardson shows, threatened the Northern ideology of “free labor,” and therefore (believers felt) “the core of American society.”

All of which is to say: When Lindsey Graham calls “the Squad” “communists,” he knows what he’s doing.