WITHIN THE WHITE HOUSE, the fierce struggle over limiting imported automobiles is now apporaching a decision. President Reagan is being urged to impose "voluntary" quotas on the imports from Japan -- the quotation marks indicating that the limits would in fact be involuntary, as well as legally dubious. The logic would be that a political gesture has become necessary to placate the American automobile industry, and that "voluntary" quotas are preferable to the mandatory quotas in the bills that Sens. John C. Danforth and Lloyd Bentsen are advancing. Some of the administration's political operatives argue that it would be embarrassing to the president to have to veto an auto import quota bill.

That's exactly wrong. A veto of a quota bill would constitute a dramatic demonstration of President Reagan's determination to get the inflation rate down. No one questions that import quotas would be drastically inflationary. As the popular Japanese cars became scarce, their prices would shoot up -- and the prices of the American cars, protected from any serious competition, would follow them upward dollar for dollar. The rest of the country, watching it happen, would shrug and conclude that the administration, after six weeks in office, had abandoned the struggle against inflation as too hard and too costly in political terms.

Paul Volcker, the chairman of the Federal Reserve Board, caught that point in his testimony yesterday before the House Ways and Means Committee. It's not only taxes and budgets that influence inflationary expectations. If import restraints are imposed, he observed, the signal that goes out is the opposite of price stability.

But import quotas would affect more than psychology. Under the pressure of their recent losses, the automobile companies are beginning to put some muscle into their own resistance to inflation. Instead of merely accepting the successive price increases from their suppliers, in the hope of passing them on in the customary fashion, the companies are starting to push back. After having let their wages slide up perilously high -- the average production worker at General Motors now earns, including fringes, $19 an hour -- the companies are getting sticky. The United Auto Workers have already made large concessions to Chrysler to save it from bankruptcy, and the other companies are beginning to demand similar rollbacks. It's not only at Chrysler that excessively high wages cost jobs. Resisting inflation isn't pleasant. But the alternative, for the automobile workers and everyone else, is continued slow growth, even higher unemployment and recurrent disruptive financial crises. That's the future that President Reagan was elected to change.

If the president now allows any kind of restrictions on automobile imports -- whether "voluntary" or mandatory, legal or illegal -- he will be calling an extremely damaging retreat in his campaign against inflation. He would probably describe it as a minor tactical withdrawal. It would be comparable to Napoleon's minor tactical withdrawal from Waterloo. If the president were willing to give up so much so early, people would expect much worse to come as the elections got closer. That would be, as the supply-side theorists say, a rational expectation.