Last weekend, pollsters Peter Hart and Lou Harris told 40 Democratic senators attending a retreat in West Virginia that the Democrats still don't have the credibility to challenge a popular President Reagan on economic or defense issues.

Essentially, their message to the senators was that the public needs more time to perceive that Reaganomics isn't working. They believe that the public wants the Reagan program to succeed, and that the Democrats had better shape their alternative program carefully before lashing out at him.

Economists at the retreat, including Lester Thurow of MIT, told the senators the Reagan program can't work because the over-generous tax package assures deficits and high interest rates as far as one can see. Either taxes have to be raised, some of the tax cuts must be rescinded, or the defense program must be slashed mercilessly, they said.

The senators were told by other panelists, including former Defense Secretary James Schlesinger, that Reagan's clumsy handling of the defense program could be attacked, that the devastating impact of high interest rates could be attacked, that his back-and-forth performance on Social Security benefits was open to challenge.

But the Democrats aren't in an attacking mood. Sen. Dale Bumpers of Arkansas told me, "Most of my colleagues came away with this feeling: Keep your powder dry, and don't carp at everything the administration does."

The only alternative to Reaganomics that comes quickly to some people's minds is Carternomics--and who wants that? But as I have suggested before in these columns, the Democrats are following a counsel of timidity, lying low, anticipating that the economy will go to pot, and believing that they will have time to step in and offer to pick up the pieces.

That may be politically astute, but how about the country? As former Ambassador Sol Linowitz privately asked a group of Democrats at a Pamela Harriman soiree (a transcript was leaked to the Wall Street Journal), "If the situation is as dire as you all painted it, is it responsible to remain silent?"

Democrats should be striving, it seems to me, to avert the looming economic disaster, to articulate an alternative, and to convince the public that there is something that can be substituted for both Reaganomics and Carternomics, each of which abandons the idea that economic growth is a healthful phenomenon. Now is the time, for example, to speak out against tax indexation and the "sale" of tax losses from one company to another. These are commitments made by Reagan and a weak Congress that should not be kept. The sooner the effort is made to overturn them, the better.

But if the consensus that came out of the West Virginia retreat and the evening at the Harrimans' turns out to be a guide to Democratic Party policy, Democrats will hold their fire until the country feels "the pain" that economic advisers believe will be evident after the turn of the year. To be sure, Democrats will flood the Congressional Record with pious statements of outrage on this or that issue.

But I'm not talking abut meaningless rhetoric that senators can point to later when someone asks: "Where were you when Reaganomics ran us into a recession?" I'm talking about a real, honest-to-God program that somebody believes in and will publicize and whip up some sentiment for--now. So long as Reagan can say, "What's your alternative?" he has the Democrats licked. You can't beat something with nothing.

Hart told the senators at the West Virginia retreat that Reagan had successfully kept the focus on big government, and the need to cut spending, glossing over what happens to programs and people when that spending is cut. The Democrats have played Reagan's game by trying to be even more righteous than he in displaying fiscal integrity.

"The Democrats have to get the attention back on the economy," Hart said, "and then they might stand a good chance." The Democrats, says Hart, have to spell out the kind of tax breaks that Reagan gave the privileged classes and measure them against the budget cuts. The oil companies, for example, walk away with $10, $20, or $30 billion in tax reductions, while $10, $20, or $30 billion is slashed from school lunches, student aid, job programs and other "people" programs. Finally, the Democrats have to underscore how the takeaways from poor people (to make room for the giveaways to the rich) are putting a tremendous burden on the state governments, which will have to raise taxes in order to fill the gap.

But so far, if I read the tea leaves from West Virginia correctly, those 40 Democratic senators can't get together on a program that will unify them. They are waiting for help from Reagan and Reaganomics. In short, they are still bamboozled by The Gipper, and are afraid to sound like Democrats.