YOU HAVE to be a real administration loyalist to take at face value the Pentagon's insistence that its official disclosure of top-secret information on the "Stealth" aircraft project last month was guided entirely by a desire to plug further leaks. The "major" unauthorized leak that prompted the disclosure came, in a story in this newspaper, on Aug. 14 -- just as Jimmy Carter was being renominated. Officials cited in that story acknowledged readily -- some of them bitterly -- that it was going to be used to combat Ronald Reagan's charges that Mr. Carter had lowered the nation's guard by, among other things, canceling the proposed B1 bomber. The Stealth technology, you see, is supposed to render aircraft virtually invulnerable to radar detection. It will thereby enable a future bomber to penetrate enemy defenses far better than could the late and widely lamented B1, and it will enable an administration so minded to claim that in canceling the B1 it was merely, wisely, waiting for a penetration bomber that actually could penetrate.

Secretary of Defense Harold Brown and President Carter resist conceding outright that the Stealth announcement was intended at least in part to burnish the administration's controversial defense credentials. Mr. Carter has a particular problem: to be seen as an adequate (but not excessive) hawk, but not to be seen as a born-again hawk. But the administration's collective denials are lame. It evidently wants the credit for demonstrating urgent and effective concern for security, but it does not want the blame for whatever damage may have been done -- political damage as well as security damage -- by premature release of secret information for campaign purposes.

Ronald Reagan says the Pentagon's confirmation gives the Soviet Union a tip-off of 10 years (lead time for a Stealth-equipped bomber) to prepare countermeasures. What about that? It seems fair to ask why, if the offense was so heinous, it took Mr. Reagan three weeks to say so. Is it just a coincidence that his assault coincided with an evident need to lift his campaign out of something of a self-confected slump?

For all of that, we remain troubled by the possibility that the administration's confirmation that Stealth had been proven, flight-tested and validated at the highest levels did add a good deal to earlier leaks -- and to earlier official acknowledgments that the United States was working on the problem. Mr. Carter, ever since he got down to actually running against Ronald Reagan, has been doing some very transparent and occasionally reckless rearranging of his own defense record and trying to alter the public's perception of it. He has shown himself willing to involve the most intricate and secret security matters in the political campaign. The burden is on the administration to show that the Soviets, in the Stealth affair, were not handed an intelligence coup.