Thomas W. Evans, a lawyer who formed part of the team that organized Richard Nixon’s successful presidential campaigns in 1968 and 1972 and who later wrote an insightful book about the ideological transformation of Ronald Reagan, died June 11 at his home in Bay Harbor Islands, Fla. He was 82.

He had mesothelioma, his daughter Heather Evans said.

In 1967, Mr. Evans was a partner in the New York law firm where Nixon worked after his failed early bids for president and California governor. Another partner in the firm, Leonard Garment, helped bring Mr. Evans into Nixon’s inner circle.

Political historian Theodore H. White, in “The Making of the President 1968,” credited Mr. Evans, Garment and John Sears, another lawyer at the firm generally known as Mudge, Rose, Guthrie & Alexander, with persuading Nixon to run for president in 1968.

“Tom Evans and Len Garment,” Nixon wrote in his memoirs, published in 1990, “were often in my office talking more politics than law.”

Mr. Evans directed volunteer outreach for Nixon’s 1968 campaign and served as a key link between the political and fundraising operations. In Nixon’s 1972 reelection campaign, he had key roles in fundraising efforts.

After serving as an education and business adviser in the administration of President Reagan, Mr. Evans published “The Education of Ronald Reagan: The General Electric Years and the Untold Story of His Conversion to Conservatism” in 2006. The book is considered an insightful look at a little-known period in Reagan’s intellectual development.

From 1954 to 1962, when his Hollywood acting career had begun to wane, Reagan was host of the television show “GE Theater” and traveled the country as a spokesman for General Electric. Once a New Deal Democrat, Reagan became a conservative Republican during those years. His political mentor was Lemuel Boulware, a GE public relations executive who was known for his opposition to labor unions and his support of low taxes and free markets.

The philosophy Reagan espoused in his nationwide talks for GE became the core of his basic message when he entered politics in the 1960s.

“Evans makes a powerful and persuasive case that Reagan’s tenure at GE was key to his transformation into an ardent conservative,” political journalist Jacob Heilbrunn wrote in a 2007 review of Mr. Evans’s book in the National Interest. “The result is one of the most illuminating books ever written about Reagan.”

Thomas William Evans was born Dec. 9, 1930, in New York City, where his father was a business executive.

He graduated in 1952 from Williams College in Massachusetts, then served in the Marines during the Korean War, during which he received the Silver Star and two Purple Hearts.

Mr. Evans was a 1958 graduate of Columbia University law school.

He worked for the New York law firm of Simpson, Thacher and Bartlett before joining Mudge, Rose in 1965.

His corporate clients included PepsiCo and Warner-Lambert, the pharmaceutical company, and he also had a specialty in nuclear power.

One of Mr. Evans’s classmates at Williams was George Steinbrenner, who became principal owner of the New York Yankees. According to “Steinbrenner: The Last Lion of Baseball” by Bill Madden, Mr. Evans introduced Steinbrenner to Nixon’s personal attorney, Herbert W. Kalmbach, who was also deputy finance director of Nixon’s 1972 campaign.

Steinbrenner was later convicted of obstruction of justice and conspiring to make illegal contributions to Nixon’s campaign. Mr. Evans was never implicated in any of the legal troubles surrounding Nixon during the Watergate era.

In 1973, when Steinbrenner organized a syndicate to purchase the Yankees from CBS, Mr. Evans was one of more than 15 minority owners. He was the team’s general counsel for a short time before selling his share.

Steinbrenner died in 2010.

For years, Mr. Evans was a champion of educational outreach efforts, and he established a program in which lawyers mentored students in New York schools. He wrote two books on education and was counsel to the Points of Light Foundation, a volunteer service organization inspired by President George H.W. Bush.

Survivors include his wife of 56 years, Lois Logan Evans of Bay Harbor Islands; three children, Heather Evans of Bequia in St. Vincent and the Grenadines, Paige Evans of New York City and Logan Evans of San Diego; and five grandchildren.

For the past few years, Mr. Evans was of counsel in the Washington office of the Fulbright & Jaworski law firm. He was working on a memoir of his years with Nixon.