[citation needed] In 1969, Dunne became President of the Cook County Board of Commissioners, succeeding Richard B. Ogilvie, who had been elected Governor.

He was elected by a 79–1 vote of the committee, defeating a vigorous effort by Ed Kelly (47th ward committeeman and superintendent of the Chicago Park District) to secure the position for himself.

"[3] In 1982, Dunne lost the party chairmanship to alderman Edward Vrdolyak, an ally of Byrne (who had been elected mayor of Chicago in 1979.

[citation needed] After Washington's death in office later that year, Dunne played an important role in securing Eugene Sawyer's appointment as mayor by the city council.

[3] Approaching the age of 80, and enmeshed in a scandal in which he admitted having sex with female county employees[4][5] (The Chicago Tribune printed a correction that these women were not pressured into providing sexual favors to him,[citation needed]) Dunne decided to retire in 1990, and did not seek re-election to the County Board presidency or party chairmanship.

[3][6] The Cook County Administration Building at 69 West Washington Street (originally the headquarters of the Brunswick Corporation) was renamed in his honor and bears his portrait in the lobby.

His son George became an actor and musician under the name Murphy Dunne, appearing in the Chicago-based Blues Brothers movies.