THE OBITUARIES of Chancellor Helmut Schmidt's government in West Germany may have been, as the fellow said, exaggerated. His opposition still intends to try to force him out of office at the end of this week on a vote of no confidence. But Sunday's election in the state of Hesse makes that challenge infinitely more risky. Mr. Schmidt's Social Democratic party has always been strong in Hesse. But its unexpectedly good showing, and the collapse of the Free Democrats, suggest that the results of a national election are far less predictable than German politicians of all parties had been assuming.

The Free Democrats have inadvertently touched the Weimar reflex in German voters. Germans remember the Weimar regime of the 1920s and early 1930s as one in which dozens of fragmented parties struggled for power and produced a succession of unstable governments. Germans also remember what came next. Ever since World War II, regardless of any other issues and interests, Germans have used their votes consistently to punish any party that even hinted at backsliding into Weimar politics.

The small Free Democratic party put the Social Democrats into power 14 years ago by swinging into coalition with them. The coalition having worn thin over the years, and the Free Democrats having lost some of their following, they finally decided to abandon Chancellor Schmidt and swing back to the conservatives. That would bring in a new government without -- important point -- going through a nationwide election. The present German election, written with Weimar in mind, gives no seats to any party with less than five percent of the vote, and the polls suggest that the Free Democrats are teetering on the edge of that requirement. They are highly anxious to avoid elections until they have had time, presumably as partners in a new government, to fortify their position.

But the Hesse returns, testifying to the German distaste for this kind of parliamentary intrigue, raise the chance of an early election. Paradoxically, those returns also point to the possibility of a peculiar outcome--a standoff between the big parties, with the Free Democrats vanishing altogether and their place as kingmaker taken by the Greens. Although the Greens call themselves environmentalists, they are in fact an anti-political movement of radicals and free spirits bound loosely together by causes as various as support for clean air, hostility to industrial development and religious pacifism. Many of them are young people who, unlike their parents, have no memory of Weimar. It may take more than one election to return German politics to the stability to which voters there are accustomed.