Richard Donohue and family visit President John F. Kennedy in the Oval Office on Aug. 15, 1963. (Cecil Stoughton/John F. Kennedy Presidential Library, Boston)

Richard K. Donahue, a Massachusetts trial lawyer and confidant of the Kennedy political dynasty who served as president of the sportswear company Nike in the early 1990s and later saw his law license suspended after becoming embroiled in a tawdry courtroom saga, died Sept. 15 at his home in Lowell, Mass. He was 88.

A son, Richard Donahue Jr., confirmed the death but did not cite a cause.

A third-generation lawyer in Lowell, a longtime industrial city north of Boston, Mr. Donahue forged an enduring connection to the Kennedy political machine as a young man. He grew active in grass-roots organizing that spurred John F. Kennedy’s rise in the 1950s and early 1960s from congressman to senator to president.

In 1960, Mr. Donahue worked in primary battlegrounds such as West Virginia, a largely rural and Protestant state where Kennedy’s Catholic faith was seen as cause for concern in his bid for the White House. As a riposte, he raised Kennedy’s World War II record aboard PT-boat 109.

As Mr. Donahue later told journalist and author Robert Sullivan, “I would get a call, ‘They’re murdering us here with the Catholic stuff.’ And I would say, ‘Hit ’em with the 109.’ West Virginia had the greatest percentage of gold-star mothers, really proud of what their sons had done in the service. That started to help.”

Kennedy’s triumph over Sen. Hubert H. Humphrey (Minn.) in the primary was a vital hurdle in securing the Democratic nomination for president. Mr. Donahue was later described in journalist Theodore H. White’s “The Making of the President 1960” as “a coruscatingly brilliant young lawyer,” prompting Kennedy to quip, “50,000 votes the other way and we’d all be coruscatingly stupid.”

In Washington, Mr. Donahue held the title of assistant to the president, and his portfolio included patronage appointments and serving as a liaison to Congress.

With an eighth child on the way — he and his wife would have three more — Mr. Donahue resigned from the White House in mid-November 1963 for a more lucrative private practice back in Lowell. He left a week before Kennedy was assassinated in Dallas.

He went on to have a distinguished legal career in Massachusetts, serving as president of the state bar association and chairman of the state Board of Bar Overseers, a disciplinary committee. By the late 1970s, his political background brought him to the attention of Nike, the Beaverton, Ore.-based company that was growing rapidly amid a national fitness craze.

The president of the Oregon Bar Association asked Mr. Donahue, with his Washington connections, to help “this little running-shoe company” resolve several matters, including its payment of exceedingly high customs fees to the U.S. Customs Service.

“If it weren’t for JFK, I probably wouldn’t be associated with Nike at all,” Mr. Donahue told Footwear News.

Over the next decade, as a company director, Mr. Donahue played an active role in business decisions that guided the company’s international expansion and positioned Nike as an aggressive competitor against footwear rivals Reebok and Adidas.

Philip H. Knight, who co-founded Nike and served as its chairman and chief executive, named Mr. Donahue president and chief operating officer in 1990. At the time, the company was facing a boycott organized by the Rev. Jesse L. Jackson to spotlight what he called Nike’s poor recruitment of minorities.

Knight and Mr. Donahue suggested the attack was a setup by Reebok because Nike’s Air Jordan — endorsed by basketball star Michael Jordan — was enjoying dazzling success. In response to questioning at a news conference, Mr. Donahue said there were “some blacks in management” but could not name the highest-ranking.

Georgetown University basketball coach John Thompson Jr., a longtime Nike consultant, soon became the first black member of Nike’s board of directors.

Mr. Donahue stepped down from his public role in 1994 and remained vice chairman of Nike’s board until 2008. Soon after he left the presidency, Nike faced intensifying news reports about its labor practices, in particular sweatshop working conditions overseas.

Richard King Donahue was born in Lowell on July 20, 1927. After Navy service near the end of World War II, he graduated in 1948 from Dartmouth College and in 1951 from Boston University law school. He returned to his home town to work at his family’s law firm as a trial lawyer.

His “godparents in politics,” he later said, were Kenneth P. O’Donnell and Lawrence F. O’Brien Jr., members of John F. Kennedy’s inner circle. In 1952, they recruited him to help in the successful campaign by then-Rep. Kennedy to unseat incumbent Sen. Henry Cabot Lodge Jr., a Republican.

Over the decades, Mr. Donahue remained at the disposal of the Kennedy family. In 1980, he was a key campaign organizer for Sen. Edward M. Kennedy (Mass.), unsuccessful Democratic primary challenger against President Jimmy Carter. Mr. Donahue was later a founding board member of the John F. Kennedy Library Foundation and served as its vice chairman for nearly 30 years.

Besides wife of 61 years, the former Nancy Lawson, survivors include 11 children; two sisters; a brother; and 16 grandchildren.

Mr. Donahue’s embarrassing career capstone was his entanglement in the late 1990s with the Demoulas family, whose members had been waging a bitter fight for control of the multibillion-dollar Market Basket supermarket chain, an institution in Massachusetts.

After a state Superior Court judge had ruled against one branch of the Demoulas clan, Mr. Donahue’s role had mostly been to oversee the continuing legal strategy of the losing side in that case and handle public relations.

Two other lawyers associated with Mr. Donahue concocted a scheme to discredit the judge. They invented a sham job offer for the judge’s clerk in the hope that during job interviews, he would reveal that the judge had been biased against their client from the start.

The subterfuge went off the rails, including threats to the clerk’s livelihood. As Boston magazine later reported, Mr. Donahue had ignored many of the ethical red flags raised by members of his own team.

The Board of Bar Overseers recommended disbarment for two of the plotting lawyers and found Mr. Donahue less culpable because his role was in the planning but not the execution of the scheme. He was reinstated to the bar in good standing in 2011.