William H. Schweitzer in 2013. (Courtesy of Baker Hostetler)

William H. Schweitzer, a partner with the law firm BakerHostetler in Washington who represented Major League Baseball in the halls of Congress as one of the nation’s premier sports lobbyists, died March 3 at his home in Alexandria, Va. He was 70.

The death was announced by BakerHostetler, where he had served as managing partner of the Washington office from 1993 to 2009. The cause was a heart attack, said his wife, Leslie Schweitzer.

Mr. Schweitzer developed expertise in election law and campaign finance issues as well as sports law.

He was chiefly known as a top Washington lobbyist for Major League Baseball for the past 20 years, initially as general counsel of the American League and later working with the office of the commissioner to represent the organization’s interests in Washington. He was credited with smoothing the way for the return of big-league baseball to Washington, which lost the Senators to Texas in 1971. The Montreal Expos moved to the nation’s capital in 2005, becoming the Washington Nationals.

Beyond the action confined between the proverbial foul lines, baseball’s interests extended to questions dealt with on the federal level, including immigration, security, steroids, taxation, telecommunications and antitrust matters.

His responsibilities included efforts to keep key legislators abreast of how measures that might come before Congress could affect the game, according to the Baseball America Web site.

“His counsel was vital toward navigating our way through many challenges that the game once faced,” former commissioner Bud Selig said in a statement.

William Hoefler Schweitzer was born in Cleveland on June 6, 1944. He graduated in 1966 from Trinity College in Hartford, Conn., and in 1969 from Georgetown University’s law school. He was an assistant U.S. attorney in Washington from 1970 to 1973 before joining BakerHostetler.

The firm had long represented the American League and, according to BakerHostetler colleague Bruce Sanford, Mr. Schweitzer’s manifest affection for baseball made him a likely choice to carry on that work. “I don’t think he ever missed an all-star game or World Series game,” Sanford said. It was not that anyone required him to attend, Sanford said. He “did it with relish.”

Over the years, Mr. Schweitzer represented a variety of other clients, including Republican Party members, Harvard University and major trade associations such as the National Association of Home Builders. He spent many years as Republican counsel for the House Administration Committee.

Survivors include his wife of 42 years, Leslie McElfresh Schweitzer of Alexandria; and two sons, William H. Schweitzer Jr. of Sharon, Conn., and Arthur H. Schweitzer of Alexandria; a brother, Robert Schweitzer of Alexandria; and a sister, Barbara Lamade of Chevy Chase, Md.