No policy game in this town is harder to break into than nuclear strategy. The heavy hitters have been at it for decades, and new boys, if they are not intimidated, are customarily waved off. All the more reason, then, to take note of Rep. Albert Gore Jr., a 34-year-old fourth-term Tennessee Democrat, the latest and in a way the unlikeliest member of the club.

Exactly a year ago this week, Gore made his debut as a strategist--quietly, in the back pages of the Congressional Record. Nice, earnest, boyish-looking, former divinity and law student, ex-journalist Albert Gore. There were few ripples.

But wait. A year passes and Henry Kissinger, an original heavy hitter, comes out in Time with his "new approach" to arms control. No one can convince me, as a lot of people are now saying, that Kissinger stole it from Gore. Kissinger need coaching? Still, it is eerie how his analysis mirrors Gore's: from the key concept to the key numbers.

Gore lacks the master's experience and mystique, but that's not everything. Kissinger, for instance, as much as anyone gave us what is increasingly widely seen (even, now, by him) as the colossal error of MIRV--putting many warheads on one launcher. MIRV made the nuclear soup we and the Russians are in now. We began it, they leapfrogged us, and we're in the process of trying to leapfrog them. Kissinger manfully concedes his new package is designed to undo the damage done by his old one. The Gores do not have to apologize for being new at the game.

They do, however, have to know something. Gore had been pondering the subject a bit when, at a Girls' State meeting back home, he thought to ask if the girls expected a war in their time. Eighty-five percent of the hands went up. Could a war be prevented? Three or four hands. Gore, a strait-laced and ambitious man who happened then to be reviewing his purpose in politics, paused.

Early in 1981 he joined the Intelligence Committee, committing himself to spend at least four to six hours a week boning up. During this immersion he came upon "my conceptual breakthrough," bouncing it off experts and polishing it for a year until he felt ready to go public.

Last year, well, I meant to sit down with Gore but didn't get to it. This week I paid a call, alert for signs of the fanatic or the flake. There were none. Gore has gone beyond the catechism and is at ease with the flow of the debate. He has discipline, a readiness to listen and a hunger to persuade.

His "breakthrough": for a dozen years the driving factor has been one side's fear that the other has attained or will attain a capability to use its accurate multiple-warhead missiles to knock out the other's land-based missiles in a first strike. Whether such a strike makes military sense is arguable, but the very possibility casts a long political and psychological shadow. The fear of a first strike is the definition of strategic instability: it is what makes nukes dangerous.

Reagan's approach, reducing the numbers of weapons but improving their striking power, would actually increase instability by leaving each side with a greater ratio of warheads to land-based missile targets--with a greater fear of the other's first strike.

To brutally foreshorten it: Gore's answer is to move from multiple-warhead missiles back to single-warhead missiles. Each side would have an invulnerable deterrent but neither would have a first- strike capability--stability at last.

The single-warhead missile is the hot idea of the '80s. Gore and Kissinger are for it. The Scowcroft commission, trying to salvage a strategy from the MX wreckage, likes it. Some hawks are for it, some doves. The Soviets have nibbled: it offers them the same stability it offers us. At this point, it is still different things to different people. I will not try to sort it all out today.

My point lies elsewhere: starting from scratch, in a brief time, through personal exertion, Gore can fairly claim to have had a major role in, as he puts it, moving a central set of ideas from the perimeter of debate to the center. At a time of disarray inside the administration and dismay outside, he speaks clearly for stability, at once the prime nuclear value and the best available ground on which domestic consensus and international agreement might yet be built. Move over, Henry.