Politicians have learned to trust economists about as much as lab mice trust biologists. For some reason, they think the experiments may not do them much good.

They distrust the economists' jargon, their methods, their models, their forecasts, their switches and their equivocations. So they tend to take refuge in the fact that economists are often in disagreement with each other.

But this is one of those rare moments when the economists are leaving the politicians very little wiggle room. If the economists are wrong, they are almost unanimous in their error. And if they are right, the politicians really have no excuse not to act.

In the last few weeks, three eminent economists--all of whom have headed the President's Council of Economic Advisers--have given their views to three sets of politicians. No differences in theory, methodology or partisanship clouded their crystal balls.

Martin Feldstein, Republican and current chairman of President Reagan's CEA, gave his description in late July to the Senate Banking Committee. A few days later, Alan Greenspan, Republican and chairman of President Ford's CEA, laid it out for the National Governors Association. Ten days after that, Charles L. Schultze, Democrat and chairman of President Carter's CEA, drew the picture for the National Conference of State Legislatures.

The three speeches were so similar that you could, almost literally, move paragraphs around from one to another without anyone's noticing. This is what they said:

The powerful recovery now under way can and should continue for the balance of 1983, without reigniting the danger of inflation.

It will slow "at a fairly dramatic rate" (Greenspan), "substantially" (Feldstein) or "significantly" (Schultze) as we move into 1984 and rebuilding inventories catch up to sales.

Further economic gains may not be aborted, but will almost certainly be distorted, by the impact of abnormally high real interest rates. Those rates will damage the housing and construction industries, cripple export sales, limit the attractiveness of capital spending and investment, and leave defense and consumer products to carry the whole burden of sustaining forward momentum.

The main reason for the abnormally high, destructive interest rates, they all said, is the inability of the federal government to discipline its own spending. The seeming inevitability of annual deficits in the range of $200 billion as far as the eye can see casts a huge dark shadow on the economic horizon.

If the government could produce a realistic plan for reducing those deficits, all three economists see the genuine prospect of a golden age--a time of low inflation, real productivity growth, improved international competitiveness and economic expansion.

But as realists about Washington, Greenspan and Schultze say (with incumbent Feldstein maintaining a discreet silence) that there is no prospect of a serious political negotiation between the Republican president and Senate and the Democratic House of Representatives untill the 1984 election is out of the way.

Without such an agreement, they say, chances are we will bump along through 1984, risking almost every day a miscalculation by the Federal Reserve Board or a tremor in the world economic situation that could cut the recovery off at the knees and trigger either a new recession or a new round of inflation.

Absent an agreement, the risk factor will grow steadily until it becomes almost an inevitability.

The outlines of the needed grand compromise are clear to the economists of both parties: an agreement to slow the growth of both the defense budget and entitlement spending, combined with measures to recover some of the tax revenues squandered in the last 30 months of federal tax cuts.

Greenspan called for an "economic summit" to hammer out such a deal-- as soon as the victors in the 1984 election are reassembled in Washington in January 1985. But given the stakes for this country and the world, such a delay is unconscionable.

If we faced a military threat, or a natural disaster, no one would dare hang a sign on Pennsylvania Avenue saying, "Congress and White House Out to Lunch. Back in 17 Months."

The voters of this country do not have to accept such cavalier treatment from the politicians. Anyone who is out campaigning--and they all will be this fall, from the president on down--should be told, "before you ask my support, tell me what you are doing now to get a handle on the deficits that can destroy our future." If they don't have a good answer, tell them they've lost your support.

The economists have given the politicians no excuse. Neither should the voters.