THE 1948 ELECTION, which almost everyone expected would bring a return to Republican "normalcy," instead produced victories for Harry S Truman and for a group of talented young Democrats who gave postwar American liberalism its tone and shape. They included Adlai Stevenson and Paul Douglas in Illinois, Hubert Humphrey in Minnesota, Lyndon Johnson in Texas and G. Mennen Williams in Michigan. Mr. Williams died the other day in Detroit.

These were young men: Mr. Williams, like Mr. Humphrey and an actor named Ronald Reagan who presided over the final Truman rally in the Hollywood Bowl, was just 37 and at the threshold of what proved a long and fruitful career. An upset winner for governor that year, Mr. Williams was reelected five more times, transforming what had been one of the nation's most heavily Republican states into one that was counted as safely Democratic. Heir to the Mennen fortune (hence his nickname Soapy) and a graduate of prep school and Princeton, he campaigned by calling square dances and attending every ethnic festival he could find. He was an early and fervent supporter of civil rights, and it was his influence and that of his political allies in the United Auto Workers that enabled John F. Kennedy in 1960 to win larger percentages among black and Polish American voters in Michigan than in any other state.

The disappointments of Gov. Williams' political career anticipated some of those of liberals generally. His failure in 1959 to get a malapportioned Republican legislature to pass a progressive income tax led to a fiscal crisis that ruined any chance he had of running for president. His early support for John F. Kennedy was rewarded with the post of assistant secretary of state for African affairs, which was not considered one of Washington's plums and in which he was criticized -- it is hard to remember why -- for making the perfectly sensible statement "Africa for the Africans." He was beaten for the Senate in 1966 when both his domestic liberalism and his support of President Johnson's Vietnam War policy were liabilities.

But he showed no disappointment and persevered in seeking chances to render public service. In Michigan he was elected to the state Supreme Court in 1970 and served 16 years; he was busy with other projects when he suffered a stroke Monday. To all his work Gov. Williams brought a sweetness of character that was one of his political strengths. He was one of an outstanding class of postwar liberal politicians who worked hard to make America a better place, and in a great many ways succeeded.