“Unity” has suddenly become one of the most popular buzzwords in American political discourse. Listen to the two leading moderate Democratic presidential candidates, and you might think creating unity, not shaping policy, is the point of holding the nation’s top office. Joe Biden is running because he thinks “Democrats want to unify this nation.” Similarly, Pete Buttigieg wants our vote because he’s the candidate “who can turn the page and unify a dangerously polarized country.”

As a political goal and a campaign tactic, unity may seem like an obviously good idea. A look at American history, though, shows that unity has often meant something much less positive: coming together to preserve the status quo, no matter how oppressive or unfair.

The United States was founded on the ideas of liberty and democracy, but also on the realities of slavery and racial exploitation — and the rhetoric of unity has long been central to the preservation of American white supremacy. It’s true that calls for unity have sometimes been a bulwark against extreme racism; in the 1920s, for example, the American Unity League was an important opponent of the Ku Klux Klan. More often, however, unity has meant preserving the basic structure of racial oppression in the name of avoiding conflict between white Americans.

The link between unity and racial inequality dates back to 1776, when the Continental Congress deleted a passage from the Declaration of Independence declaring slavery “cruel war against human nature itself.” Southern delegates who owned enslaved people, and Northerners who traded them, demanded removal of the language as the price for maintaining a united front against England. More concessions to slavery followed: to get the Constitution ratified, antislavery politicians accepted passages protecting the slave trade for 20 years and declaring each slave to “count” as three-fifths of a person.

Similarly, as sectional tensions flared in the 19th century, politicians decided that the only way to preserve the union between the states was to placate white Southerners’ demands for the expansion of slavery.

The Missouri Compromise of 1820, which allowed Missouri to become a slave state in exchange for banning slavery in other territories, was hailed as a victory for national unity despite the devastating outcome for enslaved people in Missouri. “The bond of union is too strong for them,” explained President James Monroe; “great moderation, firmness, & wisdom” prevailed over demands to outlaw bondage in the state.

Thirty years later, Congress passed another compromise that opened the door to more new slave states and made it illegal to help escaped slaves even in the North. Sen. Henry Clay, author of the Compromise of 1850, justified these measures as necessary for “the satisfaction and reconciliation of the people of this country” — demonstrating that his definition of “people” did not include African Americans. Other politicians went further, offering by 1860 to guarantee the preservation of slavery with a constitutional amendment in exchange for keeping the country unified. The name this group chose for itself was the Constitutional Union Party.

In 1861, tensions over slavery led to the Civil War. But though the 13th Amendment outlawed slavery in 1865 and Reconstruction led to great strides toward achieving racial equality, political figures continued to use the rhetoric of unity to justify racial oppression. They triumphed in the disputed election of 1876, when Southern Democrats allowed Republican candidate Rutherford B. Hayes to take office in exchange for allowing racial segregation to return to the South. Hayes justified his abandonment of African American rights by insisting in his inaugural address that only “the united and harmonious efforts of both races,” not government power, could bring about racial progress.

Afterward, Northern and Southern whites reunited the country through celebrations of shared Civil War military sacrifice designed to obscure the fact that slavery had caused the war. “How complete the Union has become!” Woodrow Wilson declared at one such veterans’ reunion in 1913. “We have found one another again as brothers and comrades … the quarrel forgotten.”

Meanwhile, Southern Democrats maintained segregation for generations by using the language of unity to promote one-party rule in the South. “We white people ought to keep united,” Mississippi Sen. Lucius Q.C. Lamar thundered in an 1884 campaign speech. “Here in Mississippi unity of purpose … [is] a supreme necessity of self-preservation.”

This is why civil rights activists targeted the concept of unity in their protests. In 1963, when the Rev. Martin Luther King Jr. protested against segregation in Birmingham, Ala., eight white clergymen who claimed to oppose segregation wrote an open letter decrying King’s tactics as “unwise,” “untimely” and “extreme.” The ministers titled their letter “A Call for Unity.” King’s blistering response, in his famous “Letter from a Birmingham Jail,” was that “the white moderate who is more devoted to order than to justice” was a bigger obstacle to civil rights than was the KKK.

In recent years, some American leaders have tried to reclaim the idea of unity from its tragic history, to reimagine it as a cross-racial phenomenon in which African Americans might play a leading role. That was Barack Obama’s goal in his 2004 keynote address to the Democratic National Convention: “It is that fundamental belief — I am my brother’s keeper, I am my sister’s keeper — that makes this country work.” But there are limits even to this more inclusive vision of unity. Obama’s approach gave the United States its first black president, but not the kind of structural changes that would reduce the wealth gap between whites and blacks or end police brutality against African Americans. And the fact of Obama’s presidency itself became a rallying cry for white reaction, further showing the limits of his strategy.

As King wrote, there’s an important difference between “a negative peace which is the absence of tension” and “a positive peace which is the presence of justice.” Too often, unity offers a fantasy of harmony that ignores the pleas of the suffering or, worse, blames them for destroying the illusion of unity. In such cases, the more pressing question is: Who is benefiting from unity, and at whose expense?

Americans should be wary of politicians who promise unity without committing to the hard work of achieving social change. Unity in an unjust world might mean not having to argue with friends and families over basic human rights and equality — but it also means that promises of equal rights and dignity go unfulfilled. For some, unity feels good because it suggests that daily interactions will involve less conflict. But when unity is prioritized over justice, injustice reigns.