The truth has a biological advantage. It doesn’t need the artifice of man to survive. It lives and breathes freely on its own.

Seventy-eight-year-old Essie Mae Washington-Williams recently confirmed one of the oldest rumors of Southern political folklore: that she is the mixed-race daughter of former Sen. Strom Thurmond.

Williams, whose mother worked as a maid in the Thurmond family home, was long rumored to be Thurmond’s daughter. In a 1968 book, writer Robert Sherrill alleged that Thurmond had fathered a mixed-race child. In 1972, the front page of a local South Carolina newspaper announced that Thurmond fathered a “colored offspring.” In 1992, The Washington Post referred to Williams as Thurmond’s “supposed daughter.”

During the senator’s lifetime, Thurmond’s family and staffers repeatedly denied the claim, describing Williams as a friend of the family. Through my long working relationship with the senator, I know otherwise.

There was a conversation that occurred at a 1996 Washington Urban League ceremony honoring myself and Sen. Thurmond for the growing bonds between black and white Americans. Back stage, Sen. Thurmond leaned over and said, “You know, I have deep roots in the black community — deep roots.”

His voice softened into a raspy whisper: “You’ve heard the rumors.”

“Are they just rumors, senator?” I asked.

“I’ve had a fulfilling life,” cackled Thurmond, winking salaciously.

The subject came up again while the senator and I were attending a S.C. State football game in Orangeburg. He mentioned how he had arranged for Williams to attend S.C. State College while he was governor. (Sen. Thurmond caused a stir when his official car rolled onto campus for a visit.)

“When a man brings a child in the world, he should take care of that child,” said Thurmond, who then added, “she’ll never say anything and neither will you — not while I’m alive.”

Thurmond showed me where she lived while attending S.C. State and admitted to helping her out financially. Though he didn’t say outright that Williams was his daughter, the senator’s remarks left little to interpret.

Then there was a private conversation we had a few years back. The senator had been frequently ill at the time and given to random bouts of nostalgia. He mentioned how proud he was that he was able to maintain a close relationship with Williams.

Beaming with pride, he talked about how she called him and sometimes took him to task when she didn’t agree with statements he made. Perhaps he saw some of his own tenacity reflected back in her. Thurmond also talked about the disconnect between what politicians sometimes espoused publicly during the de jure segregation era and what they did in their private lives.

This point was not lost on civil rights leaders, who collected pictures of Williams on campus to use as political ammunition against Thurmond, a noted segregationist at the time.

But Williams never confirmed the rumors. For 78 years, she honored the senator’s request that no one know the truth about their relationship. During his lifetime, she placed the senator’s political career above her own well-being. So why is she coming forward now?

Williams has not made any financial claims on Thurmond’s estate. “We are not looking for money. We are merely seeking closure by way of the truth for Essie Mae Washington-Williams,” said her attorney, Frank Wheaton, to The Washington Post. After nearly eight decades of subverting certain basic and essential facts about her identity, it seems that Williams wishes to be honest with herself — and society — about who she is.

This is a good thing. Now that the senator’s personal indiscretions can no longer be used against him, there is a moral obligation to set the historical record straight.

After all, the history of Sen. Thurmond is inextricably bound up in the story of Southern politics. In 1954, he became the first person elected to the U.S. Senate by write-in vote. His 24-hour filibuster on a 1957 civil rights bill still ranks as the longest speech ever on the Senate floor. In all, Thurmond’s political career spanned seven decades, making him the longest-standing public official in our country’s history.

The senator’s story is our history. Now that Sen. Thurmond has passed on, history deserves a full accounting.

Mr. Williams, a native of Marion, hosts “The Right Side with Armstrong Williams,” a nationally syndicated talk-radio program.