From Franklin Roosevelt's unprecedented New Deal through Jimmy Carter's unlamented New Foundation--the Democrats were America's dominant political party. The Democrats initiated and they innovated, setting the nation's agenda with noble visions as well as with impractical schemes. During that period, the Republicans were mostly political remaindermen, heirs to those the Democrats alienated and occasional beneficiaries of Democratic excesses.

But the GOP was not monolithic. The party split into two separate and warring camps: the "Skins" and the "Shirts." The Skins, with their major following in the West and the South, opposed outright what the New Deal and the Great Society proposed, branding those Democratic designs as unneccesary, probably unconstitutional, and surely un-American. By contrast the Shirts, with their strength in the Northeast and upper Midwest and including in their camp most descendants of the Mayflower passengers, did not reject the New Deal in its entirety. The Shirts' line was: "We could have done what had to be done at 10 percent off and with people who went to better prep schools."

Now, less than a year before they name their presidential nominee at the San Francisco convention, the Democrats are generally playing the part of the Shirts in our national politics. President Reagan (himself an authentic Skin) is setting the national agenda and dominating the national debate. To the president's bold policies in taxes and spending, the derivative Democrats are mostly reacting: "Not quite so fast, please, on the tax cuts and the budget cutbacks. We could do it all with more "fairness" and compassion.

Without a shared vision of their own to offer the country, the Democrats must hope for opposition errors big enough to return them to the White House.

It is not too late for the Democrats to consider the thoughtful advice of a practical politician, Peter Hart. He is now polling for Walter Mondale, but his advice could be heeded by the entire party. Democrats won in 1982, according to Hart, on the theme of "it's unfair, it's Republican." But for 1984, their economic policy must be one of growth and not simply of distribution. Democrats must offer a way to enlarge the economic pie. Second, says Hart, Ronald Reagan misread his own election as "meaning a blank check for the Pentagon." But the Democrats must define America's role in the world by first answering two questions the pollster poses: what will we do to protect our interests? What will we do to make the world a safer place?

Next, the Democrats must define the proper and legitimate role of government. They must show, Hart says, they have the "toughness to govern" to go along with the "compassion to care." The Democrats must recapture from the Republicans the values of, as he puts it, "God, flag, and family." Most important of all, Democrats cannot try to win by assembling constituencies through specific appeals that add up to 50.1 percent of the vote. There must be an "appeal to the greater national interest." Peter Hart is right.