What's new, Democrats?

Some long-time Democratic strategists are expressing a strange pre-election worry: that their party will win big. The worry then becomes that Democrats will draw the wrong conclusions: that they can sit back with their traditional politics and wait for Reagan Republicanism to destroy itself.

Such an outcome could confirm the view that the so-called decline of the party system in the United States is mainly the decline of one party, the Democrats.

Recently there have been enough ''me-too'' Democrats in the House of Representatives to give the Republicans most of what they wanted. Last year came the phenomenon of congressional Democrats pushing corporate tax breaks even beyond what a Republican administration proposed.

But me-too is not where the future of a party lies, as the GOP discovered when the Democrats were riding high. It lies in developing alternative policies and convincing voters that they are better.

To be sure, some voters for Democrats may be saying that they do want a return to the traditional Democratic effort to spread the nation's abundance through strong federal action. But the growth to provide abundance can no longer be taken for granted. So party thinkers now stress both growth and equity in the search for alternatives.

They see that the old form of platform-making is not enough - listening to what all the interest groups want and then adding it together. They are looking for the overriding public interests that citizens have in common whatever the subgroups they belong to. They see economic tribulations tending to make citizens recognize their common interests - so that membership in a special interest group takes a secondary role.

One thing retained from New Deal/Fair Deal/Great Society days is a conviction that the federal government still has a leading role to play. But it is cast more as a partner than as a boss of the private sector.

Thus the need for national coordination in achieving growth is addressed not through the kind of ''planning'' agency found in some competitor nations but through an economic cooperation council. This body would monitor economic change, assess strengths and weaknesses, provide a center to clarify complex choices and arrive at wise decisions.

The council is one of the specific recommendations in the recent report of a task force on long-term economic policy sponsored by the Democratic Caucus in the House of Representatives. The report calls for an ''investment strategy'' not just in plant and equipment but in:

* The human capital of skills and education, with every student ''technically literate'' in computer-age terms by the end of the decade, for example.

* The deteroriating roads and other infrastructure of the country, with a program to inventory of needs and determine what combinations of public and private resources can best meet them.

* The energy resources and conservation to reduce vulnerability to foreign oil suppliers, with such options as a gasoline tax to help support the effort.

* The basic and new industries to preserve America's competitive edge, with an economic environment created to encourage private investment and a national research effort to keep ahead in new technologies.

Are voters as much interested in alternatives as the Democrats who have been at work on them not only in Congress but at the midterm party conference last June, in policy study groups, and in the offices of individual campaigners? The question should be clearer after Nov. 2.