He marched with the Rev. Dr. Martin Luther King Jr. He is credited with helping John F. Kennedy become president of the United States, and he cofounded the Peace Corps.

And in 1991, Harris Wofford became Pennsylvania’s first Democratic U.S. senator in a generation.

Mr. Wofford, 92, died Monday at George Washington University Hospital from complications after a fall in his Washington home Saturday morning, according to son Daniel.

Mr. Wofford served in the Senate from 1991 to 1995. He was appointed by Gov. Robert Casey to fill a vacancy caused by the death of Sen. John Heinz and subsequently won a special election to finish the term.

But he was perhaps better known for what he did during a long career in public service before he arrived in the Senate.

A lifelong activist, Mr. Wofford advised Kennedy on civil rights. A world traveler and major booster for volunteerism, he also directed AmeriCorps under President Bill Clinton, and helped establish the Martin Luther King Day of Service.

President Barack Obama recognized Mr. Wofford in 2012 with a Presidential Citizens Medal, the country’s top honor for civilian service.

Well before Mr. Wofford pursued elective office, the self-described New Deal Democrat was known as a civil rights activist who participated in King’s 1965 march from Selma to Montgomery, Ala. Mr. Wofford was among the first whites to graduate from the Howard University Law School.

Working on Kennedy’s 1960 presidential campaign, Mr. Wofford arranged a meeting between the candidate and King. And when King was arrested for participating in an Atlanta sit-in, Mr. Wofford advised Kennedy to call and offer sympathy to wife Coretta Scott King.

That call has been credited with helping swing the election in Kennedy’s favor, after word of the gesture spread through black communities nationwide, helped by leaflets on blue paper the campaign quietly distributed at Mr. Wofford’s direction.

Kennedy carried the African American vote with an estimated 70 percent, a bigger margin than the party typically won at the time. Some polls had found Republican Vice President Richard M. Nixon leading among black voters in 1960.

“It is thought by many that that one phone call started the transformation of the Democratic Party,” said James Carville, who was Wofford’s campaign strategist in 1991 and later worked for Clinton’s campaign.

After the 1960 election, Mr. Wofford served as Kennedy’s special assistant on civil rights before leaving the White House to help R. Sargent Shriver, the president’s brother-in-law, found the Peace Corps.

After Heinz died in a plane crash in Lower Merion, Casey appointed Mr. Wofford, the state secretary of labor and industry, to the seat after a 35-day search.

Acknowledging he hadn’t been the governor’s first choice, Mr. Wofford quipped to reporters that he also may not have been the “first choice” of his wife, Clare, “but we’ve been going strong for 43 years."

Republican Dick Thornburgh, the U.S. attorney general and former governor, began the race with a 44-point lead in the polls, but Mr. Wofford prevailed. He won by tapping into the anger that many in Pennsylvania felt about politicians in Washington during a recessionary time, Carville said. “Harris Wofford, the most unlikely insurgent in the world, became the insurgent," Carville said. “The country was looking for something else.”

Mr. Wofford made a national health-care system the centerpiece of his campaign. He often cited a doctor who argued that if everyone accused of a crime is entitled to a lawyer, Americans also should have access to doctors. That idea became a TV commercial.

His health-care push foreshadowed Clinton’s successful run for president the following year. The Clinton campaign considered Mr. Wofford as a possible running mate.

Sen. Bob Casey Jr., the late governor’s son, said Mr. Wofford’s victory helped trigger the Clinton administration’s early work on health care.

“Harris’ election was a very clear indicator that people really wanted health care,” Casey said. “Not only did he have a sense of where the nation should go on an issue, but he was willing to dedicate a substantial part of his life to advancing it.”

“Most public officials, public servants, would want to accomplish a third of what he accomplished and consider themselves highly successful,” Casey added.

“The lesson that I got from him is that important change requires a long march and persistence and perseverance," said Daniel Wofford, referring to the struggles for civil rights and access to health care.

Mr. Wofford ran unsuccessfully for reelection in 1994 against Republican Rick Santorum, an aggressive conservative who helped the GOP take control of the Senate (it also captured the House) in a midterm reaction against the Clinton administration’s first two years. Using the health-care issue, Santorum portrayed his opponent as a relic of the 1960s big-government era.

In 1970, Mr. Wofford had become president of Bryn Mawr College, a position he held for eight years, and later he became chairman of the Pennsylvania Democratic Party.

Jim Brown, onetime chief of staff to both Caseys, described Mr. Wofford as a person who was “ahead of his time,” from his work on advancing civil rights to his commitment to public and social service.

“People would meet Harris and they would think, ‘He’s not realistic. He has his head in the clouds,’” Brown said. “But think about the things he worked on that later came to fruition — the civil rights work, the Peace Corps, the larger theme of volunteerism. They say a life well-lived — his was well-lived and effective.”

Harris Llewellyn Wofford Jr. was born on April 9, 1926, in New York City.

He grew up in a Republican family in Scarsdale, N.Y., and at age 12 took a six-month trip around the world with his maternal grandmother.

Recounting the trip in a 2013 interview with the Inquirer, Mr. Wofford said he saw “Mussolini take Italy out of the League of Nations, thundering from his balcony" in Rome.

"We saw Gandhi in the streets of Bombay,” he said, and walked through the rubble of Shanghai after it had been destroyed and captured by the Japanese.

In his later years, he would take his grandchildren on trips abroad.

Mr. Wofford was in high school when the Japanese attacked Pearl Harbor, and he founded a group called Student Federalists, which aimed to create a federal world government that would resolve global conflicts.

As president of the organization, he traveled to Minnesota and met his future wife, Clare, according to their son. They married in 1948.

Mr. Wofford volunteered for the Army Air Corps at age 17 and served stateside through the end of World War II.

He graduated from the University of Chicago, and from Yale Law School in addition to Howard’s. Early in their marriage, the Woffords traveled to India, ultimately writing a book together, India Afire.

It was there, his son said, that Mr. Wofford was introduced to Mohandas K. Gandhi and the idea of nonviolent civil disobedience.

That experience “awakened him to the race issues in America,” Dan Wofford said.

Mr. Wofford sent King a copy of the book in April 1956, along with a letter in which he suggested that “some straight Gandhian civil disobedience” could help defeat bus segregation, according to records maintained by the Martin Luther King Jr. Research and Education Institute at Stanford University.

Clare Wofford died in 1996 after a struggle with acute leukemia.

In 2016 Mr. Wofford married Matthew Charlton, a man 50 years his junior, with whom he had been living for 15 years. They had met on a beach in Fort Lauderdale, Fla., and had felt what Mr. Wofford called an instant attraction to one another.

“Too often, our society seeks to label people by pinning them on the wall — straight, gay, or in between,” Mr. Wofford wrote in the New York Times. “I don’t categorize myself based on the gender of those I love. I had a half-century of marriage with a wonderful woman, and now am lucky for a second time to have found happiness.”

In addition to his husband, Mr. Wofford is survived by daughter Susanne; another son, David; a brother; a sister; and six grandchildren.

Plans for services were incomplete.

Staff writers Angela Couloumbis, Susan Snyder, and Jonathan Tamari contributed to this article, as did Liz Navratil of the Harrisburg bureau.