The transformation of President Carter from cold-eyed critic of the Soviet military takeover of Afghanistan will come into focus in a few days when the world learns his intention to reduce real defense spending from levels established before the rape of Afghanistan.

The fine print of the new anti-inflation budget will belie much of what Carter told the nation in his celebrated State of the Union address on Jan. 23. Instead of the 5 percent "real" defense increase he pledged then, the budget as now taking shape inside the White House will show a spending increase only about 1.5 percent higher than the rate of inflation.

"I'm determined that the United States will remain the strongest of all nations," Carter said to rousing applause on Jan. 23. Two days later, Gen. Richard Ellis, top commander of the Strategic Air Command, quietly revealed to the House Armed Services Committee that the United States now is on the short side of what he called an "adverse" balance of strategic strength -- long-range nuclear missiles.

Yet despite the president's pledge and the general's testimony that Moscow's new strategic margin frees it for military actions without the old worry over U.S. reactions, Carter plans to reduce the real rate of defense spending from the pre-Afghanistan level. He will blame this transformation -- from matching to ignoring Soviet power -- on the need for a balanced budget, Carter's front-line weapon in the battle against soaring inflation.

In fact, however, the decision to cut back defense spending as a budget-balancing aid, while Soviet military spending continues its non-stop rise in real growth at an annual rate of 4 percent, is perceived by some politicians and military analysts as more ominous than its stated target -- balancing the budget.

These Carter critics believe that the president's State of the Union rhetoric rallied the nation around the flag -- and Jimmy Carter -- at immense political cost to Sen. Edward M. Kennedy, that it was more political than intellectual. Kennedy is Carter's only competitor in the Democratic presidential campaign.

Supporting the critics are important pieces of evidence that point strongly to this conclusion: some powerful members of the Carter administration genuinely doubt that the United States can match Soviet military power, strategic or conventional, in the foreseeable future, if ever.

Indeed, as we reported in the spring of 1978, one of the key technical advisers on Zbigniew Brezinski's National Security Council staff, Victor Utgoff, privately questioned the wisdom of U.S. strategic superiority but went a long step further by adding, almost as an afterthought: but "we cannot afford to allow ouselves to drift into significant strategic inferiority." Some "inferiority," in other words, was quite acceptable.

Now, almost two years later in an international climate far rougher than then, another White House aide shocked a senator last week during a talk on U.S.-Soviet relations held in the senator's office. The White House staffer said that the Soviet Union is now producing military weapons on what is virtually a "mobilization or wartime footing" that is simply beyond U.S. capacity to match.

Carter's apparent willingness to hold down defense spending, on grounds that it is a major budget-balancing tool, flatly contradicts this careful statement made by Defense Secretary Harold Brown last Dec. 13: "Should our assumptions as to future inflation . . . later prove to have been underestimates, the administration will take appropriate action to preserve the integity of this program."

The sudden spurt in the rate of inflation is why Carter should be making major additions to his defense budget -- if he and Brown really meant what they said. Confidential estimates from the Office of Management and Budget to key congressional committes show no such additions. Just to keep the pre-Afghanistan budget intact, for example, Carter needs to ask about $7.5 billion in new money for the fiscal year starting Oct. 1.

This display of presidential decision-making has its counterparts. Right after the Afghan invasion, promises were made with fanfare to arm Pakistan. But the amount of money offered, military experts uniformly agree, was too paltry for Pakistan to take the chance of alienating Moscow. The whole deal dissolved into embarrassing thin air.

Likewise, a series of proven underground Soviet nuclear tests believed by the United States to violate the test-ban treaty, the latest on Dec. 23, have gone unchallenged by the United States.

The most likely explanation is found in that same transformation of Jimmy Carter that has turned him from a pledged advocate of strong defense to a Pentagon budget-cutter: he truly does not perceive the Russians as dangerous enemies but as partners, with the partnership momentarily distracted by Afghanistan.

Under this theory, widely held by the president's critics, the transformation of Jimmy Carter was not his move toward military budget-cutting; it was his unaccustomed tough talk right after the Soviet move into Kabul. What is now coming into view, then, is the real Jimmy Carter following a very brief metamorphosis.