Whoever would have suspected, listening to the campaign broadsides on the evils of government spending, that Ronald Reagan would, within a few years, have the distinction of presenting the nation's first trillion-dollar budget?

Think of Lyndon Johnson, turning out the lights in the White House and all that, in the fruitless quest to keep the 1965 budget below $100 billion. Think of Arthur Burns, desperately urging that the 1971 budget be held under $200 billion -- and now, one trillion dollars. Cap Weinberger must simply blanch as he contemplates the projections. When the nation ripped through the half-trillion-dollar mark in FY80, it was the spendthrift Democrats who were in charge. For Harry Hopkins in the Great Beyond, the mere thought of a trillion dollars to spend must be simply mouthwatering. Yet this remarkable orgy in political finance is to be wasted on those who do not even enjoy government spending.

The shame of voting out a trillion-dollar budget ironically enough will descend on those new senators who, with NCPAC support, campaigned against high government spending. Poetic Justice? Both ways. The Bayhs, the Nelsons and the Culvers would certainly have reveled in a trillion dollars of public spending.

How did we get here? In part, it was easy. Given inflation, the gross national product is now rising at $300 billion a year, and the budget by $60 billion a year -- without the unpleasant necessity of producing any more goods or services. In such an environment, talk of restraining nominal government expenditures has an oddly hollow sound.

At $579 billion, the 1980 budget has just come in -- a paltry $47 billion above the original estimate. This impressive record may yet be matched in the 1981 budget. While the 1980 budget overruns may have reflected both hope and honest error, the 1981 budget has been wholly disingenuous from the first -- based on the election-year desire to pretend that the budget might come into balance. It would take a miracle to prevent the final numbers from soaring over $650 billion -- strikingly above the roughly $613 billion in the budget and the First Budget Resolution. That also implies that the 1982 Carter budget, if it is honest, must come in at close to three-fourths of a trillion dollars -- an impressive level achieved even before the green-eyeshade types of the Reagan era appear on the scene.

It will be tempting for the Democrats in Congress to punt, either by not passing or by introducing cosmetic cuts in a new budget resolution during the lame duck session -- so that the apparent orgy of fiscal extravagance will be revealed only after the start of the new era of austerity. Unquestionably, such inaction would mesh well with the strategy for the 1984 campaign. A trillion-dollar Reagan budget -- after all the campaign revelations of the horrors of government spending -- is sufficiently juicy material to serve the opposition in the next campaign, in precisely the same role that the "misery index" served in this campaign.

What are the temptations for the Repulbicans?

The transition budget chairman -- an old colleague and one of my favorite people -- Cap the Knife, aghast at the nation's ruined finances, is now whetting his famous blade behind the scenes. The temptation is quite simple -- given entitlements outlays soaring at $40 billion or more a year -- to plunge the dagger into the soft underbelly of Defense, still a-quiver from the tender mercies of the Carter years.

Preposterous -- given the Repulbican commitment to strengthening the nation's defenses? Hardly. One can already hear the sounds of scuffling backstage -- no 7 percent (or 6 or 5) real defense growth, no $20 billion add-on to the Defense budget at this time.

In terms of domestic politics, of course, it makes sense. Fiscal responsibility. Financial prudence. Capital formation. The condition of the money and capital markets. Above all, the public remains overwhelmingly concerned about inflation. Inflation probably did more than either the hostages or a flaccid foreign policy to turn this election. What if the inflation rate is still close to 10 percent in 1984? And the Thatcher government, no less dedicated to the security of the West than is the incoming administration, has already led the way in fighting inflation by shortchanging defense.

Yet to yield to the temptation would be catastrophic. The international chickens of the Carter era would then come home to roost on Reagan's shoulders. Security is the prerequisite for everything else -- political rights, standard of living, economic progress, economic stability. Our military forces have been allowed to decay. Our international position is the most perilous since the Battle of Midway.

Our allies overseas -- nations free and unfree -- see in the Reagan victory the prospect, the possibility, of serious American rearmament. It would be a mighty signal -- long overdue. It is the necessary condition, if not a sufficient condition, for patching together the stability of the non-Soviet world now under threat. The United States must now set a course in which other nations can see in the years ahead the restoration of the power balance. They are now waiting -- hopeful, though dubious. If we fail now to renew our strength, the nations of Europe and the Middle East will have the worst of their fears confirmed about a United States no longer willing to fulfill its international role and will continue in their desperate search for alternative arrangements to preserve their security.