As West Germany's ''hot fall'' heads for its climax this month: * The conservative government thinks it has basically won on the issue of starting deployment of new United States missiles in December if Soviet and American negotiators fail to reach an accord at Geneva.
* The opposition Social Democrats are hastening toward rejection of new deployments - and possibly a serious split in the party.
* A discouraged peace movement is feuding in its own ranks about the use of force in antinuclear demonstrations.
All these developments are important. As West Germany goes, so goes NATO.
If initial West German deployments of the intermediate-range missiles proceed relatively smoothly, NATO will breathe a sigh of relief.The concurrent initial deploy-ments in Italy and Britain will be quite manageable, NATO planners say, given the lack of any strong antinuclear movement in Italy and a certain public disenchantment with the peace movement in Britain.
The Netherlands probably can't be brought along to fulfill its missile commitments for the mid-1980s, but perhaps Belgium can, and that will be sufficient to demonstrate NATO's resolve and unity to the Soviets, the reasoning goes.
When Helmut Kohl came to power in Bonn a year ago, the initiative in the missile debate clearly lay with the opponents of deployment. Outgoing Social Democratic Chancellor Helmut Schmidt was constantly on the defensive - especially within his own party - in supporting NATO's ''two tracks,'' i.e., deploy the new missiles if nothing came of arms control talks.
Now the initiative lies instead with the supporters of deployment.
Although more than 60 percent of West Germans don't want new missiles even if arms control talks fail, almost 60 percent are nonetheless willing to deploy if the Soviet Union doesn't remove its intermediate-range nuclear missiles, according to one poll. It all depends on how the question is asked.
Typically, the missiles have just not been a major issue among voters, either at the general election last March or the two state elections at the end of September.
The recent US flexibility at the Geneva negotiations - and the recent Soviet refusal even to apologize for shooting down a passenger airliner - have helped reinforce this indifference. So has the sophistication of West German authorities in dealing with September's warm-up demonstrations.
If tolerating the new missiles characterizes the current public mood, however , it manifestly does not characterize the Social Democrats' current mood. To the distress of Mr. Schmidt's pragmatic wing of the party, one state party caucus after another has been denouncing new deployments without waiting for the results of the Geneva talks, which are due to end in mid-November.
The pressure of ''responsibility'' on a party in power no longer applies to the Social Democrats. It was only Chancellor Schmidt's threat to resign that kept the last two party conventions behind NATO's two-track decision. With this restraint gone, the regional organizations have felt themselves freed from a straitjacket.
By now it is doubtful whether the pragmatists can even hold the November convention back from a sweeping denunciation of NATO's planned land-based missiles by, say, advocating an alternative of sea-based missiles that would not be on German territory.
Already the old pragmatist-left-wing split is beginning to reappear in the party, after a year and a half in sublimation. The pragmatic faction - to which shadow chancellor Hans-Jochen Vogel belongs - took Dr. Vogel sternly to task in early September for weak leadership on the missile issue, according to two participants in the meeting. And the pragmatists' anger at party chairman Willy Brandt is said to be even stronger, though this has so far been kept out of the German press. In varying degrees, both Vogel and Brandt have tried over the past year to make common cause with antinuclear voters to the left of the Social Democrats.
As for the peace movement, it will probably get a record turnout of more than 1 million at the Oct. 22 high point of antinuclear demonstrations. But it is patently not going to prevent the deployments. And it has had only modest success even in enlisting the important trade-union movement to its cause.
The Trade Union Federation planned for members to down their tools for five minutes today in a generalized show of support for peace - repeating similar gestures in the past for such causes as solidarity with suppressed East German workers or German reunification. But the federation has turned down a general strike for peace.
Given this lack of impact, some of the antinuclear activists are urging more militant actions to jar the public into greater concern about missiles. Some of the counter-cultural Green legislators have said they do not rule out illegal actions against property as distinct from persons. They would approve, for example, the theft of missiles if that were possible.
At the latest attempt at a public dialogue - between West German officials and representatives of the peace movement at a Lutheran academy in Loccum - the militants won out at the end of September. Activists who call themselves ''autonomes'' physically blocked access of invited speakers to the hall.
The more pacific demonstrators oppose such action as counterproductive in alienating the man in the street from the antinuclear cause. But there are enough of the ''autonomes'' - whose main aim often seems to be trashing the police - to keep the pot boiling.