The Reagan "zero option" for theater nuclear weapons in Europe was a master stroke. It put the Soviets clearly on the defensive and unilaterally disarmed Europe's unilateral disarmers.

But can it last?

All too often when we make an offer to the Russians, they simply stare back. The pressure then builds to modify our proposal to get the stalled talks moving. President Reagan, in fact, has criticized past administrations for wanting to reach arms agreements with the Russians so badly that they chipped away until the agreement was more Russian than American. That was the heart of Reagan's opposition to SALT II.

This pattern is almost certain to be repeated by Ronald Reagan himself. While the Russian negotiators won't face any obvious pressures, the U.S. negotiators will. First, when the negotiations start to drag, the pressure cooker on the European left will start to build. Marches and demonstrations will pick up. European governments will nudge us to make another offer. "The zero option was only an opening offer," they'll say. "You can't really expect them to remove all their SS4s, SS5s and SS20s." Second, a decision on deploying our Pershing II and cruise missiles in Europe is to be made in the summer of 1983. The approach of that deadline will bring pressure for more concessions.

German Chancellor Helmut Schmidt will play a major role. He first raised doubts about the U.S. nuclear guarantee--the fear among Europeans that if the Russians attacked Europe with missiles the United States might not respond for fear of a Soviet attack on North America. That led to the idea of deploying nuclear missiles in Europe to show our commitment and to trade for removal of Russian missiles.

The European political atmosphere has now changed markedly. Anti-nuclear elements have strengthened all across Europe--not to mention right inside Helmut Schmidt's own party. Schmidt must face a party conference on deployment before the deployment decision is made.

Schmidt is a very strong individual, but his country needs d,etente, his party needs to avoid a battle over deployment, and he needs an agreement to remain chancellor. These pressures could well cancel Pershing II and cruise missile deployment, while the Soviets emerge with most of their missiles and few constraints.

This outcome may well appear, even to Schmidt, a meager result for so major an undertaking. It may be politically defeating for Reagan (not domestically, but internationally) as he emerges with a handful of crumbs from what he described as a banquet.

It is none too early to be thinking of moves to turn the outcome more toward our favor. Two come to mind:

1)We should be looking at ways to increase our European nuclear forces that are not politically sensitive. One possibility is to place more weapons at sea. That was rejected in 1979 because it didn't link U.S. forces closely enough to Europe. But with the renewed activity on Europe's left, the political climate has changed.

2)We should be pressing the Europeans to build up their own conventional forces. In a debate that never involved the general public, the NATO governments in the 1960s reluctantly accepted the American "flexible response" strategy. That meant we would respond to any Soviet attack in kind--a conventional attack with conventional weapons and a nuclear attack with nuclear weapons. This policy was more honored in the breach than the observance. European governments, looking over their budget numbers, continued to rely on American nuclear deterrence and gave short shrift to their own conventional forces. There was no public debate on this or on the natural result-- our buildup of an arsenal of more than 7,000 nuclear weapons in Europe.

If the Europeans want to reverse field and stop relying on nuclear weapons, that is their privilege. But Europe should realize that means heavier outlays for conventional forces or no defense at all. The demonstrators in Europe are unified in opposition to nuclear weapons in Europe-- not only the Pershing II and cruise missile, but the thousands of nuclear artillery shells and mines and rocket warheads stored there as well. The demonstrators now see the issue as simply nukes versus no nukes. Unless they want no defense--and few fall into that category--they need to recognize that the real issue is no nukes and higher defense budgets versus nukes and lower defense budgets.

Quite simply, the protesters' beef is more with their own governments than with the United States.

For the United States, the issue is our 300,000 troops in Europe. If we emerge from this exercise with neither nuclear modernization nor higher defense budgets in Europe, a proposal to withdraw our troops would go through the Congress like a prairie fire. That is not just an emotional reaction. U.S. troops must be able to protect themselves--if not with nuclear weapons, then with more allied conventional support. If neither is there, then it might be prudent to bring the troops home.

If we emerge with an increase in Europe's conventional forces, a few constraints on Russian missiles, an increased deployment of nuclear weapons at sea and a more stable coalition of support for NATO in Europe, then we will have made a good deal, even if we give up all the Pershing IIs and cruise missiles to get it.