Beginning next year, Virginia probably will no longer have one of the most conservative delegations in Congress, thanks to Tuesday's elections which saw at least three of the 10 seats -- and probably four, when the counting is completed -- go to Democrats, who previously held only one. In the Old Dominion, as well as throughout the nation, this was a mixed blessing of sorts, not only for Democrats, but also for blacks, who played an integral role in many of the Democratic victories.

But what next? Getting good strong returns from those triumphs may be as hard for blacks as formulating a true alternative to Ronald Reagan will be for Democrats. Both were indeed negative victories of sorts and both point out some of the limitations of politics in recent years.

Despite their strong election showings, both Democrats in general and blacks in particular are floundering without answers right now, and neither is likely to have an agenda soon unless they take some dramatically different steps in the future.

In both cases, yesteryear's successes begat today's vacuum. With the New Deal, the Great Society and the Civil Rights acts, the Democratic Party essentially addressed the most dramatic grievances of the past 50 years. The black agenda of the past was a natural one that grew out of the prevailing racism, and over the decades, blacks have addressed that agenda brilliantly, if not totally.

Today, neither blacks nor Democrats have a "natural" agenda as they did in the past. A new agenda must be formulated, based on new realities and new ideas. But it's much harder because not only are the problems grayer and more subtle, but they're harder to articulate and make understandable. We've reached a period of history when the answers aren't all that plain.

Discuss poverty in the abstract, for example, and the strongest reaction you can unearth from many Americans is a big yawn. They know that 20 years ago, half the blacks were poor, but today two-thirds are not poor, however tenuous their condition. They know, too, that before Reaganomics, all but 10 percent of whites had moved from the ranks of poverty. Still, any black agenda must focus on the fact that over one-third of America's blacks are still poor in this rich country. But how do you take that abstract problem and make it a concrete part of a focused agenda that will stir action?

"Politicians are bankrupt because many of their own agenda items have either been met or found to be wanting and they are looking for ideas," says Eleanor Holmes Norton, a liberal Democrat, Georgetown University law professor and former head of the Equal Employment Opportunity Commission under President Jimmy Carter.

The Democrats won by attacking Reaganomics, but now they openly admit to the difficulty of coming up with an appealing alternative, and broad internal differences will likely make it hard to form a consensus. It perhaps is easier to get blacks to vote against Ronald Reagan and his party than anything else. Beyond that, however, black leaders in most instances have tried valiantly, but have failed to address effectively black concerns in a positive sense. The issues are complex and the answers elusive.

The Democratic Party has begun to address its need for new ideas through organizations such as the Center for National Policy, a Democratic think tank headed by Cyrus Vance. One of the closest things blacks have to a think tank is Washington's Joint Center for Political Studies, which is encouraging such thought, despite limited funds.

One of the best concrete efforts blacks have made in that direction was the alternative budget drawn up last year by the Congressional Black Caucus, which proposed to balance much of the fervor of the civil rights movement with the new fiscal and political realities. Yet few Democrats took it seriously, and it was voted down 322 to 86. Perhaps that mood will change when the winning Democratic warriors from Tuesday's battles come triumphantly to Washington early next year in search of ways to make good on their promises.

Tuesday's message from blacks and Democrats is clear--correct the course of Reaganomics, which is running roughshod over many in the old coalition, especially blacks. The challenge to the leadership is to figure out how, and in many respects, getting the political mandate is the easiest part.