There must be a thousand Kremlin- and Washington-watchers who would have loved to be a fly on the table when Mr. Reagan sat down with Soviet Ambassador Anatoly Dobrynin at the White House barbecue last weekend.
The sudden revival of talk of an arms parley has caught many by surprise - inside the White House and outside. Conventional wisdom held that the Kremlin would give Reagan the cold shoulder on negotiations until the election. No one can be confident just how the latest proposal by the Soviets, to initiate antisatellite weapons talks in Vienna in September, will fare.
Both sides seem to be improvising. The proposal came up suddenly. The Reagan administration reply, linking such talks to the intermediate and strategic arms agendas interrupted in Geneva, seemed a way to mollify hard-liners as well as to say, ''Yes, we want to see you in Vienna after Labor Day.''
Any prospect of widened talks with the Soviets in September has to help Mr. Reagan politically. That need not be dwelt upon. And it would be fruitless to try to fathom what if any political calculation the Soviets may have made about the United States election; signs point to stresses and strains inside the Kremlin over what to do with the boisterous and assertive Reagan administration, just as the internal White House struggle to direct policy is incessantly waged. Certainly this latest Kremlin offer is not of a piece with the Soviet and East-bloc decision to boycott the Los Angeles Olympics.
For the West, what is most important through this period ahead is what it will reveal of Mr. Reagan's basic commitment to arms talks and getting on with the Soviets. That's the nuance that the fly at the barbecue might even have swapped Redskin Super Bowl tickets to have heard.
Arms control tends to have its own life, through unending private talks among experts, without a direct presidential role. It's been difficult to know, through Mr. Reagan's 31/2-year term, who speaks for the administration. Is it Richard Perle or Fred Ikle at the Department of Defense, George Shultz at State, Robert McFarlane at the National Security Council? The stable of spokesmen has often seemed to exercise a presidential prerogative without direct presidential guidance.
A lot is at stake at this moment on arms. A momentum for policy usually builds before an administration takes office. This was true of momentum for the SALT treaty and detente, which preceded Richard Nixon's coming to office.
Mr. Reagan can start now to set the tone and pace of negotiations for a second Reagan administration, or the domestic and diplomatic conditions for a Democratic successor.
The pragmatists in the White House appear to be on the winning side of late. It was the President himself, at a June press conference, who seemed to open the door for a look at the antisatelite issue. The administration now talks about a wide range of diplomatic exchanges on cultural and other issues. A lot of careers are on the line. How a next administration will be staffed will depend a lot on the public commitment Reagan makes during the campaign ahead.
Sitting down with Dobrynin, the President himself for the first time had the chance to talk directly and quietly with a Soviet listener about where he stands on the arms issue. If he is now viewing the issue as important to his place in history, as current evidence might suggest, the Kremlin would do well to take his interest seriously.