The puzzling last-minute Soviet initiative in the Geneva Euromissile negotiations makes sense in terms of West German politics. On the eve of planned NATO missile deployments, the Soviet move helps West German opponents of the deployment blame Washington for the failure of nuclear arms control.
This is the tentative analysis of Western diplomats in looking at one of the more curious developments in the Euromissile debate - and its connection with last week's Social Democratic Party (SPD) convention and this week's parliamentary defense debate in West Germany.
If the latest Soviet move contributed to SPD readiness to give Moscow the benefit of the doubt in arms control and place all burden of proof on the United States, they say, then Moscow can be well pleased with its achievement in West Germany.
Former Chancellor Helmut Schmidt warned his SPD colleagues in vain against such Western disunity.
''When the Eastern superpower can compel solidarity by its allies (in stationing new missiles on their soil),'' he told the Nov. 18-19 SPD convention, ''then the West must display voluntarily the necessary solidarity with the West's leading power (to maintain Europe's defense).''
As it can now be pieced together, the chronology of events relating to the Soviet move looks like this:
On Thursday, Nov. 17, news of a fresh Soviet arms control offer was published in the Frankfurter Allgemeine Zeitung. This leak, apparently from Bonn government sources, was a West German exclusive. Moscow, it was reported, would drop its insistence that the 162 French and British (primarily sea-based) nuclear missiles be counted against Soviet land-based medium-range missiles - if the US would waive altogether its imminent medium-range NATO deployments. The Soviet Union would then reduce its current 360 triple-warhead SS-20s to 120 SS- 20s in Europe and a roughly equal number in Asia.
This would leave the Euromissile balance sheet (ignoring Asia) at 120 Soviet SS-20s (with 360 warheads) vs. 162 British and French national nuclear warheads and no American NATO missiles. The Soviets would then require further compensation for the British and French missiles in some other arms control negotiations.
What was not said in the Frankfurter Allgemeine leak - but was disclosed later by the US State Department - was that chief Soviet negotiator Yuli Kvitsinsky had tried to get American negotiator Paul Nitze to present the Soviet proposal as Washington's own.
It was never clear why Moscow thought Washington would want to make a proposal so unfavorable to the West. The offer would have left Moscow with far more warheads than the West; banned American NATO Euromissiles altogether; and, in effect, counted the British and French missiles twice.
Nor, at time of writing, was it clear in Bonn where an alternative report came from saying that the Soviet Union had offered an East-West European balance of 120 warheads without counting British and French missiles. The London Observer attributed this report to a TV interview by West German Chancellor Helmut Kohl. But Kohl never gave these figures in the interview mentioned. The alternative report has fed speculation that a power struggle is under way in the Kremlin, with dove and hawk factions making and retracting arms offers.
On Friday Soviet Defense Minister Dmitri Ustinov said that the British and French missiles still had to be counted in any Euromissile arms control talks. At the same time, Soviet diplomats began telling Western colleagues that it was Washington rather than Moscow that had made the new offer (as Kvitsinsky had urged Nitze to do and Nitze had in fact refused to do).
On Friday also the Soviet ambassador to Bonn delivered a letter from Soviet leader Yuri Andropov to Kohl denying that Moscow was ready to discount British and French missiles in the Euromissile balance.
On Saturday, in an historic shift, the West German Social Democratic Party at its Cologne convention overwhelmingly rejected the new NATO deployments.
The SPD clearly would have voted against the new NATO deployments in any case. Since being released from the discipline of government a year ago, the party has rushed into enthusiastic rejection of the NATO missiles. It bases its nein on the contention that US President Reagan is trigger-happy and has not negotiated seriously in the arms control talks.
The latest Soviet moves, however, gave the Social Democrats additional reasons for their rejection of the new missiles. Thus, SPD defense spokesman Karsten Voigt argued in the corridors of the party convention that US negotiator Nitze had favored pursuing the latest Soviet offer but had been overruled by the Reagan administration. And deputy party chairman Horst Ehmke circulated a statement saying if there were a new Soviet offer it would only underscore the rightness of the SPD call for further negotiation without deployments.
Meanwhile in Washington on Saturday the US State Department issued an unusual rebuttal of the Soviet version of the exchange. In this statement it disclosed Soviet negotiator Kvitsinsky's approach to Nitze.
Nitze, according to diplomatic sources in Bonn, was furious when it became apparent that the Russians were trying to hang their own proposal on him, in a parody of the rather more serious Nitze-Kvitsinsky ''walk in the woods'' of 1982 . The sources saw this as another Soviet attempt to make informal compromise offers (often to West German contacts) without actually presenting them at the negotiating table. That way, Moscow gains credit in European public opinion for a flexibility it has yet to demonstrate in the Euromissile talks themselves.