Once upon a time, liberals were the folks who wanted to change society. They thought existing institutions were unjust and that individuals needed protection against the workings of the market. They looked forward to a society that would be different.

To a considerable extent, 20th century liberals achieved many of their goals. Racial segregation was abolished. An economic safety net was constructed. Government-issued regulations were set up to protect the environment. Few Americans want to undo these changes. But they may want others.

Looking back on election year 2004, I am struck by how many of the constituencies supporting Democratic candidates oppose, rather than seek, change – how they are motivated not by ideas about how to change the future, but by something like nostalgia for the past.

Take black Americans, the most heavily Democratic constituency – 88% to 11% for John Kerry in the 2004 NEP exit poll. Blacks have been voting for Democratic presidential candidates by similar margins since 1964, when Republican Barry Goldwater opposed the Civil Rights Act.

That was a big issue, then. And never mind that a higher proportion of Republicans than Democrats voted for the bill in Congress – Goldwater did oppose it. But the Civil Rights Act has long since become uncontroversial, racial discrimination disapproved and integration of schools, workplaces, and of public accommodations widely accepted. Yet 40 years later, the image of the Republican Party as unsympathetic to equal rights for blacks seems to persist. Black voters seem still focused on a moment in history 40 years ago.

Or look at the anti-war constituency, an important part of the Democratic coalition in 2004. These voters denounce the war in Iraq in much the same terms, with much the same arguments, that they denounced, or have heard that their elders denounced, the American military effort in Vietnam. We’re in a quagmire, committing atrocities, doomed to failure.

Right down to the signs and slogans, antiwar rallies seem a re-enactment of the tie-dyed past. In the waning days of the campaign, Mr. Kerry and John Edwards slyly suggested that George W. Bush would bring back the military draft.

The war in Iraq is different from the war in Vietnam in so many respects that it is hard to know where to start listing the ways. But for some large portion of Democratic voters, it will forever be 1968.

On the economic front as well, Democrats seem to be looking more to the past than the future. The Social Security system as it exists is obviously not sustainable: There will be too few workers supporting too many retirees. It will be in good shape, some Democrats argue, until 2042, so there is no need to worry for it. But people who turn 67 in 2042 were 29-year-old workers and voters in the 2004 election. An argument that concedes that Social Security will be in trouble when they reach retirement age can hardly be expected to appeal to them. But these Democrats see no need to change a system created in 1935.

The feminist left is an important constituency within the Democratic Party. But once again most of the change it celebrates has already been achieved. Discrimination against women is prohibited, and sexual harassment punished. Abortion rights remain firmly established in law, although the number of abortions has been declining since the early 1990s.

For younger women, the grievances of feminism must seem antique. They were told as they were brought up that they were under obligations to leave the workplace to raise their children and to subordinate their own happiness to their duty to others. On the contrary, they may have resented the absence in their daily lives of their working mothers or the divorce of parents who decided to seek happiness their own way.

The evolution of liberalism from a forward-looking to a backward-looking creed is partly the result of success – and partly a result of a failure to see where liberal ideas would lead. History does not always move in one direction, and if it seemed headed left a half-century ago, it seems headed the other way now.

An ever-larger state to protect workers may have seemed a good idea in the 1930s or 1950s, but by the 1980s it seemed clear it would strangle economic growth. Opposition to the exertion of American power looks less attractive after the fall of the Soviet empire. The advance of democracy in Latin America, East Asia, and Eastern Europe make it clear that America has, on the whole, been a force for freedom and democracy. The left is left with nostalgia.