Former U.S senator Harris Wofford, right, with his fiance, Matthew Charlton, in Nantucket, Mass. Wofford and Charlton are to marry on Saturday. (Courtesy of Harris Wofford via Civic Documentaries)

Harris Wofford, a former Democratic senator from Pennsylvania, John F. Kennedy’s presidential assistant on civil rights and an intimate of Martin Luther King Jr., will wed at his Foggy Bottom apartment Saturday before a gathering of family and friends. Dinner is to follow at a neighborhood Italian restaurant.

The groom is 90.

The other groom, Matthew Charlton, is 40.

Wofford went public with his impending marriage in the essay “Finding Love Again, With a Man” published in Sunday’s New York Times.

“Most of my life has been with a great woman, a great love, and a great family,” says Wofford at his Washington home in his first interview since the article appeared. “Now, I’m with a great love late in my life.”

Wofford is well aware that it is the age difference, more than his fiance’s gender, that has caused jaws to plop and unleashed a fusillade of social media blasts.

“Everyone has a certain kind of amusement when there’s a big age difference,” he says, seated in a rattan chair in the apartment that the couple, who have been together for 15 years, have shared for the past six. “But that’s a part of the magic of love. It really can bring people across a bridge, or build a bridge that you can cross.”

The age difference “is sort of funny sounding,” he says, “funny with a emphasis on fun.”

Tall and courtly, Wofford has been an idealist for social justice his entire life. In many ways, his public declaration of marriage at age 90 to another man can be seen as one of his last and most deeply personal acts in furthering the cause of equal rights.

Wofford attended Howard Law School in the 1950s, becoming, he believes, the program’s first white graduate. (He has law degrees from both Howard and Yale.) He helped establish the Peace Corps. In the Senate in the 1990s, he championed universal health care and later worked with several nonprofit organizations on national service and volunteering. In Philadelphia, he introduced then-Sen. Barack Obama before his 2008 “A More Perfect Union” speech on race.

Wofford worked for weeks on the essay. He wanted to share his love with the public, he says. He appears to have devoted less time to finalizing details of the wedding, which will be attended by about 30 friends and relatives, including all three of his grown children and four of his six grandsons. The couple will honeymoon and host another party at the family home on Nantucket this summer.

Remnants of Wofford’s April 9 birthday party — confetti, a banner and boxes — clutter the dining area. Quite frankly, the apartment is nowhere near ready for nuptials this weekend.

On Monday, Wofford and Charlton were still debating the readings for the ceremony. Charlton, an interior designer, was in New York working on a major assignment, although he hoped to buy the rings. Wofford plans to wear a suit.

“It’s always been a commitment since we first met,” says Charlton by phone the next day. “For almost the first 10 years, despite the distance — he was in Washington and I was in Florida — we traveled to see each other every month. Love prevailed. We’ve stayed committed to each other since we first met.”

Like Wofford, he disregards the age difference between them.

“Regardless of age, of differences, getting married is a testament of love,” he says. “It’s been an amazing time these past 15 years, pretty remarkable. Marriage is another step. It’s a confirmation. Why wouldn’t you want to marry the person you have fallen in love with?”

The grooms are keeping their own names, “though Charlton would be very nice,” says Wofford.

The former senator dismisses the assigning of labels, or “pinning,” as he calls it.

“Did I ever consider myself gay? No. It’s what I think should not be asked of people,” he says. An Old World-style romantic, he discusses the relationship in terms of love rather than sexuality.

“I think this is an example of the most private matter. Most of us are intrigued with the sexuality of friends or others. Perhaps with some close friends you want to talk about this,” he says. “When people want to talk about their sexuality, either go to confession or be happy about it. I don’t measure myself or my friends by their sexuality.”

Wofford in the Foggy Bottom apartment he shares with Charlton. (Marvin Joseph/The Washington Post)

When he first got married — in 1948, at 22 — to Clare Lindgren, the local St. Paul, Minn., newspaper observed, “The young couple are active in the movement to save the world.”

In their first year of marriage, the Woffords traveled to India on a fellowship to study the work of Gandhi: “It shaped my life,” says Wofford. They both returned with amoebic dysentery. The cure was arsenic injections for two to three months. The doctor told Clare, “This is marvelous medicine: An ounce will cure you, but 10 ounces will kill you.” Clare responded, “That’s just about what I think about civil disobedience.”

Clare, Wofford’s “best friend and my best critic,” died in 1996 of acute leukemia. She remains a constant in Wofford’s conversation, as though she were busy in the next room. After her death, “I was sure I would never again feel the kind of love Clare and I shared,” he says.

Five years later, there was Charlton on a beach in Fort Lauderdale, Fla.

Wofford was 75 and Charlton 25. At dusk, gazing east toward the Atlantic, Wofford recalls, “We had a wonderful talk, very stirring, a beautiful sky and a beautiful ocean.”

Later, he found himself thinking, “I would really like to go back to the beach and swim with Matthew Charlton again.”

It took him all of a week, possibly two, to know that this was love.

“I was surprised in the sense that I didn’t think it was likely that there would be someone that really struck me with a spark, that moved me, because of my age,” he says.

Initially, their professional interests differed, “though we shared a love of ad­ven­ture and travel, and being outdoors.” Charlton, a native of South Carolina, first studied industrial design before pursuing interior design, and he created a three-legged “Charlton chair” fashioned of metal and wood.

“He’s now got a lot of interest in politics,” says Wofford. “And I’ve come to respect and be intrigued by the design field, not that I have anything to contribute.”

Wofford and Clare Lindgren at their 1948 wedding. (Courtesy of Harris Wofford via Civic Documentaries)

Wofford possesses an unforced elegance — in the 1930s, he joined his grandmother on a six-month world tour — and is genial and generous, opening his home to a stranger days before the wedding.

He asks to be addressed as Harris. “I haven’t been ‘Senator’ for ages,” he scoffs. A former president of Bryn Mawr College and chairman of Pennsylvania’s Democratic party, he has stuffed his apartment with books and photos of Kennedy and King, Clinton and Obama, and George H.W. Bush (“I really grew to admire him”). An oversize bust of Socrates dominates the library that Charlton designed and that serves as their office.

Often on the premises is 20-something Jacob Finkel, who has been working on a documentary about Wofford for eight years. “Entirely his idea,” says Wofford. Finkel has assumed the role of assistant and gatekeeper. When Wofford’s stories take an engaging peregrination, he often turns to Finkel to prompt his memory.

For three years, Wofford didn’t share his romance with his children, who are all older than Charlton.

“If I’d been wiser, I would have gotten them to know each other a little sooner,” says Wofford, the only time he grows wistful. “When they did get to know him, they all liked him.”

“I think it’s wonderful,” says Susanne Wofford, a Shakespeare scholar and a dean at New York University, who will serve as “master of ceremonies” (her father’s phrase) at Saturday’s nuptials. “My father is a very lucky man to find someone who cares about him. They’re both very lucky.”

There was no need to get married, to make an honest man of them both, but June’s Supreme Court decision in Obergefell v. Hodges moved the couple to make their union legal. Wofford is particularly taken with Justice Anthony M. Kennedy’s majority decision and Obama’s reference to the “dignity” of marriage.

“For a long time, I didn’t think it would be politically possible. And I was wrong,” he says. “And it was wrong that I was wrong.”

A few months ago, in the living room where they are to be wed, Wofford asked Charlton to be his husband.

Charlton was so taken aback that “I asked him to repeat what he had asked, and I said yes, absolutely,” he says.

“We will find out how long I’m around and how it strengthens our great relationship,” says Wofford. “I’m very lucky to have the privilege of having had two great loves in one life.”

For the second and final time, he is thrilled to be a groom.