Debates over the filibuster tend to get theoretical fast. It’s there to protect minority interests, defenders say. Without it, majorities will run rampant. Lost in the back-and-forth is the reality of how the tool has been used so often in practice: to delay, if not destroy, legislation that promotes racial equality.

From the end of Reconstruction until the passage of the Civil Rights Act of 1964, the only bills killed by filibuster were those dealing with civil rights.

For all the invocations of high-minded principles, the pattern is unmistakable. Again and again, white Southern senators, afraid of losing their accustomed seat atop the racial hierarchy, beat back progress with the blunt instrument of unlimited debate, or at least the threat of it. They nearly took down the Civil Rights Act, too. That failure ushered in the nation’s first true experiment in multiracial democracy. But the Southerners still had the filibuster, and soon they had their revenge.

In the late 1960s, the country was on the verge of dumping the Electoral College and switching to a national popular vote for president. A relentless campaign by reformers in Congress had succeeded in convincing 80 percent of Americans to back a direct vote. National organizations with little else in common — including the American Bar Association, the Chamber of Commerce and the League of Women Voters — were on board.

The effort got a last-minute boost from the chaotic 1968 election, in which the segregationist third-party candidate George Wallace nearly deadlocked the race and forced it into the House of Representatives. Americans everywhere agreed that this 200-year-old relic was going to destroy the country.

In September 1969, the House voted overwhelmingly, 338 to 70, to approve a constitutional amendment abolishing the Electoral College. Surveys suggested as many as 30 states were ready to ratify, and several more appeared to be on the cusp.

Even the most stalwart opponents of a popular vote had resigned themselves to the likelihood that this was an idea whose time had come. The amendment stood an “excellent chance” in the Senate and a “better-than-even chance” in the states, wrote two conservatives in The New York Times Magazine.