Remember Walter Mondale? To refresh your recollection, he's the former Democratic vice president who -- as the losing candidate for president last year -- warned that Ronald Reagan would eventually have to raise taxes to reduce the budget deficit to something acceptable.

Mondale was hooted down by voters, and castigated by politicians within his own party who thought that coming out boldly for a tax increase -- as he did -- was a dumb thing to do.

But now comes Reagan's Office of Management and Budget director, David A. Stockman, with a seemingly irrepressible instinct to let his real feelings creep out.

On June 5 Stockman made a speech to the New York Stock Exchange board. He said the federal budget deficit had swollen to such proportions that, despite highly touted deficit- reducing packages on Capitol Hill, "when the books close on this fiscal year next Oct. 1, we will have run up another $200 billion in national debt; the deficit will have exceeded 5 percent of GNP for the third successive year."

He added: "As a policy matter, it is obvious enough that to close this threatening $200 billion budget gap, we must either massively cut spending or raise taxes by large, unprecedented magnitudes -- or, by the lights of some, enact a sweeping mixture of both."

If the maximum spending cut in both defense and nondefense spending is no more than $30 billion to $35 billion (which was Stockman's estimate of the Democrats' House budget proposal), responsible people would have to "acknowledge that $20 billion to $25 billion in higher taxes are then necessary to hit the minimum deficit reduction that is consistent with fiscal sanity."

And echoing his admission, in William Greider's famous Atlantic Monthly article of 1981, about "cooking the books" in makineconomic forecasts, Stockman noted that "accounting gimmicks, evasions, half-truths and downright dishonesty" had been used in preparing budget numbers and arguments. If the Securities and Exchange Commission rules applied to the agencies making such estimates, "many of us would be in jail," he said.

He attacked the House budget proposal as being "riddled with gimmicks and phony savings." And even the administration-backed Senate budget proposal, which claims a $56 billion cut in the fiscal 1986 deficit, "rests on some pretty optimistic assumptions about the path of our economy over the next three years."

Stockman's speech was to the directors of the Exchange, their wives, and other guests, including a handful of senators and congressmen. It was not off the cuff, but was a formal text not intended for release. It showed up in The New York Times, after which copies were made available.

Although Stockman press aide Ed Dale says The Times violated an understanding that the speech was intended as "background," The Times took the position that no speech of this kind to a room full of people, including politicians with a keen interest in the budget, could have or should have remained "off the record."

Like many other observers, Stockman is convinced that the unending streak of budget deficits in view for the next decade is ruining the national economy: "Our books as a nation are wildly, dangerously and intractably out of balance -- a condition that is fundamentally threatening to our economic and political health at home and our leadership and strength abroad."

Stockman last January argued that the president, having pledged in response to Mondale that he would not raise taxes, was justified in fashioning a deep slash in spending. Stockman wanted to eliminate a host of programs running from the Jobs Corps to the Small Business Administration. In addition, he wanted to cut spending for education, child nutrition, Medicare and Medicaid.

As a politician, Mondale instinctively knew that neither Republicans nor Democrats would buy that kind of curtailment of government services. In his speech, Stockman acknowledged that the spending-cut process wasn't accomplishing enough, and if the grimmer economic forecasts of the nation's leading economists are correct, "for our side there will be yet another altar call: even more spending cuts, or an acknowledgment that a last-resort tax increase is in order."

In fact, a bipartisan move is under way to include a revenue "component" in the deficit reduction package, making it possible for Democrats to support the proposed reduction in the Social Security cost-of-living adjustment. This new idea, which would create a deficit-reduction package in the $60-billion-plus range (assuming a tax increase of around $10 billion), may be publicly endorsed by Federal Reserve Chairman Paul A. Volcker.

This may be only the small beginnings of a trend toward tax increases, but I bet it's enough for Fritz Mondale to be grinning from ear to ear.