Last Saturday, an 18-year-old white man murdered 10 people and wounded three others using an AR-15 in a Buffalo food market. The shooter traveled more than 200 miles to get to a predominantly Black neighborhood, where he put on heavy body armor and live streamed his attack as he gunned down people grocery shopping. Eleven of those he shot were Black.

The Buffalo police commissioner, Joseph Gramaglia, said, “The evidence that we have uncovered so far makes no mistake that this is an absolute racist hate crime. It will be prosecuted as a hate crime. This is someone who has hate in their heart, soul, and mind.”

Before his attack, the shooter published a 180-page screed on Google Drive. It is mostly a list of his weaponry, but in it he also explained his belief in what is known as the “great replacement theory,” embraced by white nationalists. This is the idea that white people are losing economic, cultural, and political power to Black people and other people of color. The name is usually associated with a French agitator who argued in a 2011 book that immigrants were destroying European culture, but the theory that an “other” is destroying traditional society has roots stretching far back in European history. In the twenty-first century, that theory has launched right-wing political parties and shootings around the world.

But the Buffalo shooter’s ramblings drew not only from the European theory—although there is plenty of that in his 180 pages of racism and anti-Semitism. They also drew from America’s own version of a theory of replacement.

That theory comes out of the 1870s and was explicitly connected to voting.

In 1867, Congress began the process of recognizing the right of Black people to have a say in their government. In the Military Reconstruction Act, it called for conventions in former Confederate states to write new state constitutions and permitted Black southerners to register to vote to choose delegates to those conventions. White supremacists scoffed at the idea that formerly enslaved people and those white men willing to work with them could produce coherent constitutions.

When their constitutions not only were coherent, but made adjustments to give more representation to poorer white men than the prewar constitutions had provided, white supremacists set out to make sure voters did not ratify the new constitutions. Needing to avoid the U.S. Army, still stationed in the South to protect Black people and their white allies, the white supremacists dressed up in white sheets to look like dead Confederate soldiers (no one was fooled) and tried to terrorize voters to keep them from the polls.

It didn’t work. Voters ratified the new constitutions, which guaranteed Black voting. Congress readmitted the southern states to the Union, but not until they ratified the Fourteenth Amendment to the Constitution. That crucially important amendment dissolved the state laws discriminating against Black Americans. It established that Black people were U.S. citizens and guaranteed that the U.S. government would see to it that no state could take away the rights of any citizen without the due process of law.

In 1870, white politicians in Georgia tried to undermine their new state constitution. The American people then ratified the Fifteenth Amendment protecting the right of Black men to vote. Congress also created the Department of Justice to enable the federal government to enforce the Fourteenth Amendment, which it promptly did. Attorney General Amos Akerman, a former Confederate who had become a Republican, oversaw more than 1000 cases against the Ku Klux Klan.

With the federal government holding them to account for their racist attacks on Black Americans, southern white supremacists began to argue that their objections to Black equality were actually about voting. By 1871, they argued that Black men voted for leaders who promised roads and hospitals and schools. Those social investments would require tax levies, and since the Black population was poor almost by definition after enslavement, those taxes would fall almost entirely on the white men who owned property. In this telling, Black voting was essentially a redistribution of wealth from those with money to those without, from white men to Black men. It was socialism.

White supremacists began to say that they objected to Black voting and to the governments Black people elected not on racial grounds, but on economic ones. They promised to “redeem” the South from the profligate state governments that they said were bleeding tax dollars out of white landowners to provide services for the poor, generally characterized as Black, although there was no racial monopoly on poverty in the post–Civil War South.

In 1876, the “Redeemers” took over the southern states, thanks partly to the rhetoric that made them sound reasonable to northern observers and largely to the violence that enabled them to keep Black men from the polls. The “Solid South” would stay Democratic until Arizona Republican senator Barry Goldwater, running for president on a platform that called for the federal government to leave states’ racial discrimination alone, won five deep southern states in 1964.

The violence of the 1876 election, along with fears of what their lives would look like in its wake, led Black Americans to leave the South in a movement known as the Exodus. In 1879 and 1880, about 20,000 Black southerners went west to Kansas, Oklahoma, and Colorado. “[T]he whole South…had got into the hands of the very men that held us slaves,” one recalled, “and we thought that the men that held us slaves was holding the reins of government over our heads…. [and] there was hope for us and we had better go.”

About two thousand of those migrants went to Indiana.

Indiana was a contested state in which the Republican and Democratic parties traded power. In 1876, it had gone to the Democrats by a few thousand votes.

When Black Americans began to come to their state, Indiana Democrats immediately howled that the Republicans were importing Black migrants to shift the state back toward the Republicans in the 1880 election. Their clamor was loud enough to cause a Senate investigation. The Democratic majority on the select committee concluded that the Republicans must have induced the Black southerners to leave their region because there was well-paid work and no violence in the South; Republicans retorted that if they were really trying to flood the electoral system, they would have left Black Americans where they were.

But the conspiracy theory took root. White Hoosier Democrats met Black migrants with showers of rocks and vowed to “clean out all the g–d d– –n***ers in the county before the [1880] election.” After a political rally in Rockport, Indiana, Democrats attacked local Black inhabitants, shouting: “Kill them, kill them.” After they shot Uriah Webb, one rioter stood over his body and said, “One vote less,” while the others cheered Democratic presidential candidate Winfield Scott Hancock.

Racial hostility kept the Black population of Indiana small, but it also fed the cultural and social discrimination that made Indiana the beating heart of the resurgent Ku Klux Klan in the 1920s. Under violent con man David Curtis Stephenson, who raped, mutilated, and murdered a female state employee, the Indiana Ku Klux Klan developed the idea of “100% Americanism,” which argued for a hierarchy of races in which the white race was uppermost. Immigrants and Black Americans, that theory said, were destroying traditional America.

That argument has poisoned American politics since the 1870s. On Saturday, the Buffalo shooter echoed the modern European great replacement theory, but he also echoed the racial “socialist” argument of the US. He railed against Black Americans, whom he wildly insisted take, on average, $700,000 apiece from white Americans. He urged those who thought like him not to pay taxes, which he said would be wasted on such people. Then he warned white Americans not to become a political minority because minorities are never treated well.

Today’s Republican politicians, including Elise Stefanik of New York, the third ranking Republican in the House of Representatives, have pushed the great replacement theory for years and even after Saturday’s massacre have refused to denounce it. That theory is based in racial hate, but it is not only about racial hate. It is also about politics, and today Republicans are using it to create a one-party state.

“I know that the left and all the little gatekeepers on Twitter become literally hysterical if you use the term ‘replacement,’ if you suggest that the Democratic Party is trying to replace the current electorate, the voters now casting ballots, with new people, more obedient voters from the Third World,” Fox News Channel personality Tucker Carlson, who is one of the country’s leading proponents of the great replacement theory, said on his show. “But they become hysterical because that’s what’s happening actually. Let’s just say it: That’s true.”

It was not true in 1879, it is not true now, and people making this argument have blood on their hands.

Heather Cox Richardson is a Boston College history professor who writes a daily online newsletter titled “Letters from an American.”