The Civil War began over a simple question: Did the Constitution of the United States recognize slavery — property in humans — in national law? Southern slaveholders, inspired by Senator John C. Calhoun of South Carolina, charged that it did and that the Constitution was proslavery; Northern Republicans, led by Abraham Lincoln, and joined by abolitionists including Frederick Douglass, resolutely denied it. After Lincoln’s election to the presidency, 11 Southern states seceded to protect what the South Carolina secessionists called their constitutional “right of property in slaves.”

The war settled this central question on the side of Lincoln and Douglass. Yet the myth that the United States was founded on racial slavery persists, notably among scholars and activists on the left who are rightly angry at America’s racist past. The myth, ironically, has led advocates for social justice to reject Lincoln’s and Douglass’s view of the Constitution in favor of Calhoun’s. And now the myth threatens to poison the current presidential campaign. The United States, Bernie Sanders has charged, “in many ways was created, and I’m sorry to have to say this, from way back, on racist principles, that’s a fact.”

But as far as the nation’s founding is concerned, it is not a fact, as Lincoln and Douglass explained. It is one of the most destructive falsehoods in all of American history.

Yes, slavery was a powerful institution in 1787. Yes, most white Americans presumed African inferiority. And in 1787, proslavery delegates to the Constitutional Convention in Philadelphia fought to inscribe the principle of property in humans in the Constitution. But on this matter the slaveholders were crushed.

James Madison (himself a slaveholder) opposed the ardent proslavery delegates and stated that it would be “wrong to admit in the Constitution the idea that there could be property in men.” The Constitutional Convention not only deliberately excluded the word “slavery,” but it also quashed the proslavery effort to make slavery a national institution, and so prevented enshrining the racism that justified slavery. ...