The paramount question in the wake of Helmut Kohl's big victory in West Germany is whether the Russians and the Americans will grasp the nettle of arms control and negotiate an accord before the end of the year. Moscow and Washington now are under increased pressure to do so. If Moscow does not bend more, it will find NATO beginning deployment of 572 intermediate-range missiles in Western Europe in December. If Washington is not more forthcoming, it risks a wave of European antinuclear demonstrations and perhaps the polarization of Europe. The situation thus does not brook much more delay.
President Reagan is understandably pleased by the election results. It is true that the economy was the decisive consideration of voters in giving Mr. Kohl's conservatives an enlarged margin in the Bundestag. But Chancellor Kohl unequivocally endorsed the NATO missile plan, while the Social Democrats waffled in their commitment, hoping to pick up antinuclear votes. West German voters thus showed that they are willing to stand up to Moscow in the face of its unsettling military buildup and are not about to be enticed by ''neutralism.'' Indeed it should hearten everyone that the new Soviet leadership did not succeed in swaying German resolve by its overt and crude support of the leftist forces in the elections.
If the Russians ''lost'' and Mr. Reagan ''won,'' however, the US President cannot afford to be complacent. Mr. Kohl's coalition with the Free Democrats has been strengthened. But the protest party, the Greens, by winning a creditable 5. 6 percent of the vote, is a political force to be reckoned with. With a representation in the Bundestag for the first time, the Greens will not need to compromise their militantly antinuclear position, and this could mean a rise of social unrest unless the Kohl government can point to progress in the arms negotiations.
Fortunately, despite the continuing disarray in the US arms control bureaucracy, there are some signs of a willingness to compromise on the President's initial ''zero option'' proposal. More and more one hears talk of an ''interim'' solution. This would keep the zero option (no medium-range missiles on either side) as the desirable goal but achieve some reductions that would slow the nuclear arms race and serve the interests of both East and West.
That mutual concessions are possible is seen from the fact that some movement already has taken place in the negotiating positions. The Kremlin's first counteroffer to the zero option - an agreement to keep in Europe only as many Soviet medium-range missiles as the British and French have (162) if NATO abandoned its planned deployments - was clearly unacceptable. This would have left the Russians with a huge superiority in warheads. But public negotiating tactics are not to be confused with hard-boiled bargaining behind closed doors. US negotiator Paul Nitze and his Soviet counterpart Yuli Kvitsinsky did manage last summer to hammer out an ''understanding'' which was subsequently rejected by both governments. This proposal would have allowed the Russians 75 massive SS-20s with 225 warheads and the Americans 75 slower cruise missiles with 300 warheads - thus requiring the Soviet Union to reduce the number of its SS-20s now targeted on Europe and the US to forgo installation of the rapid Pershing II missiles which are capable of reaching Soviet territory in minutes.
With his hand strengthened by the German elections, President Reagan no doubt believes he can now extract more from Moscow. He is probably right. But the pressure is also on him to show that he is serious about achieving an arms control agreement - not simply to avoid the danger of political turmoil in Germany and elsewhere but because such an agreement would enhance NATO's security and peace in Europe.