Stephen W. Porter, a Washington lawyer who helped bring the Nationals baseball team to the city in 2005 and had served as chairman of the Washington Performing Arts Society, died Nov. 8 at his home in Washington. He was 80.

The cause was Alzheimer’s disease, said a daughter, Emily Gerson.

Mr. Porter helped organize and served on committees that worked to galvanize local support for Major League Baseball’s return to the nation’s capital and then persuaded MLB executives to move the Expos from Montreal to Washington, where the club was renamed the Nationals.

The Lerner family of noted real estate developers subsequently bought the team from Major League Baseball. Washington’s previous baseball team left the city for Texas after the 1971 season.

Stephen William Porter was born Feb. 22, 1939, in Milwaukee, where his father was a buyer for the New York-based Gimbels department store. He graduated from the University of Wisconsin in 1960 and from its law school in 1966. (He worked as an accountant between degrees.)

Mr. Porter began his legal career in Washington with what was then the firm of Hogan & Hartson in 1966, later moved to Williams & Connolly and in 1973 organized the firm that became Dunnells Duvall Bennett & Porter, whose specialties included real estate law. That firm was merged into Arnold & Porter, where Mr. Porter was a partner specializing in real estate until 2011, when he took of-counsel status.

Mr. Porter was a classical music enthusiast and had twice served as chairman of the Washington Performing Arts Society. In 2007, President George W. Bush named him to the National Council on the Arts. He had served on the board of the University of the District of Columbia.

Survivors include his wife of 58 years, Susan Lowe Porter of Washington; three children, Andrew Porter of Chicago, Josh Porter of Hoboken, N.J., and Emily Gerson, of Bethesda, Md.; and six grandchildren.