When the new center-right coalition voted out Social Democratic Chancellor Helmut Schmidt Oct. l, it ended a 13-year era in which West Germany finally expunged the shadows of the Nazi past and grew into European leadership. It closed the government careers, in all likelihood, of two remarkable statesmen, Helmut Schmidt and Willy Brandt. It demythologized - even as it consolidated - detente in the heart of Europe. It recommissioned the conservative architects of the German ''economic miracle'' - this time to administer a difficult economic recession.
Everyone is calling this a historic shift. And so it is. But in retrospect the most historic thing about it may be that it draws the curtain on a third of a century of historic shifts, and ushers West Germany into normal, humdrum politics.
The 13 years under Social Democratic (SPD) chancellors constituted the third age in the life of West Germany. The first belonged to conservative Chancellor Konrad Adenauer, who built up a nation from the physical, institutional, and emotional rubble of a lost war and anchored this new nation firmly to the West.
The second era belonged to Adenauer's conservative successors, who presided over the economic miracle of the 1960s that established West Germany as the leading economic power in Europe.
On this foundation the third, Social Democratic, era finally turned to deal with the unfinished business of the Hitler legacy, both at home and abroad.
Domestically, the coming to power of the Social Democrats in 1969 meant, finally, a clean break with the Nazi past. Adenauer had had no taint personally; he had refused to cooperate with the Nazis in the 1930s and 1940s. But the conservatives as a whole had not been so fastidious. And in the late 1940s the Western occupying powers, in their preoccupation with erecting a West German bastion against any Soviet expansion, had quickly dropped their ''denazification'' program and begun working with old business magnates, politicians, and some military officers without caring too much about past histories of cooperation with the Nazis.
Under the West German conservative governments, then, there was an embarrassing continuation (and promotion) of middle-level holdovers from the Hitler period, especially in the courts, education, business, the intelligence community, and the civil service.
The Social Democratic accession to power changed all this. Social Democrats had themselves been jailed and killed in Nazi Germany. Brandt had fled Germany to join the resistance in Norway. Conservative leftovers were now replaced in the intelligence agencies and the civil service.
In foreign affairs there was a parallel development. Adenauer, as an expression of penitence for German atrocities in World War II, had already instituted ''recompense'' payments to Jewish survivors of Hitler's Holocaust and to the new state of Israel. He had also begun a close French-(West) German partnership for the first time in centuries of hostile relations between the two neighbors. He had not, however, allayed the suspicions of erstwhile victims of Hitler's aggression in both East and West Europe. These people were not persuaded that the West Germans had fully renounced the past.
Willy Brandt persuaded them, by his person and by his words. Most compellingly, he visited the site of the worst Nazi extermination camp, Auschwitz, in Poland - and fell to his knees there in remorse for the brutality that had been perpetrated.
In specific policies the Brandt incumbency was marked by social reform at home and Ostpolitik abroad. In good Social Democratic tradition the social reform aimed at equalizing opportunities for all classes, at shaking up conservative orthodoxies and fairly rigid institutions.
More controversial was Brandt's Ostpolitik (east policy), West Germany's detente with Soviet-bloc countries. It was practiced under the umbrella of broader US-Soviet detente - but it still aroused conservative West German fears that it would mean a weakening of West German allegiance to the Western alliance and a dangerous flirtation with the East. It further upset the conservatives because it implied acceptance of Germany's shrunken postwar borders and recognition of East Germany - a move the conservatives had rejected in their two decades in office.
Willy Brandt carried the day, however. The four-power Berlin treaty was signed in 1971 by the former occupying powers, guaranteeing the links of West Germany with the West Berlin enclave inside East Germany, including land access between the two political entities. The Polish-West German accord was ratified. The East Germans agreed to reopen their borders to West-to-East visitors.
Most significantly, Brandt convinced the public that the practical securing of human contacts between West and East Germans was worth the cost (through the acceptance of the existence of two German states) of an indefinite postponement of German reunification. On this platform he handily won popular reelection.
So persuasive was the public mandate that the conservatives have now taken office on a pledge of fulfilling all past treaties. They will not expand relations with the East, and they will not glorify detente with the East. They will, however, preserve the degree of cooperation that now exists.
The shift from Brandt to Schmidt followed from the uncovering of an East German spy high in Brandt's chancellery. Brandt was dumped by his party (not only because of the spy, but because the oil crisis had raised new economic problems that Brandt was not equipped to handle). Helmut Schmidt, former finance and defense minister and economic whiz kid took the helm.
Schmidt carried on the Social Democratic tradition. Yet he was a Hamburg Social Democrat, a very special breed. He was sometimes referred to, only half jokingly, as the best conservative chancellor Germany ever had. He managed West Germany's economic affairs confidently - and with the trust of the business community. He became a major voice in Western economic councils and helped launch the annual economic summit of seven leading industrial democracies. He was a bulwark against protectionist pressures in trade. He, in tandem with conservative French President Valery Giscard d'Estaing, initiated the present European currency link.
Moreover, Schmidt displayed a talent for broader world affairs that won the sometimes grudging admiration of his allies. Even after the move toward a united Europe bogged down, Schmidt and his French partner still provided broad leadership for Europe in economic terms.
Under Schmidt West Germany was clearly the economic and military powerhouse of Western Europe. When there were US-European conflicts, Schmidt was often the spokesman for Europe as a whole. In periods of European exasperation with American leadership of the Alliance - or even just perplexity over the erratic American swings from administration to administration - someone was always calling on Schmidt to take over the leadership of the Western world.
In two foreign policy areas Schmidt left a particular mark - defense and East-West relations. It was his concern about a growing imbalance in the theater nuclear balance in Europe that spurred the NATO decision to deploy new medium-range missiles in the mid-1980s. At the same time it was his alarm about a breakdown in the superpower dialogue that made him insist that deployment be dependent on a real effort to negotiate arms control with the Soviet Union.
Schmidt's determination to save as much as could be saved of detente in central Europe - and of human contacts between East and West Germans - brought him into repeated conflict with Washington in the period of soured detente after the Soviet invasion of Afghanistan and Soviet pressure for a crackdown in Poland. Numerous US officials suspected Bonn of paying the blackmail of weakened allegiance to the West in a dangerous attempt to elicit leniency from Moscow.
Schmidt, on the contrary, saw his role as preventing the hardening of East-West enmity in a dangerous nuclear age into unrestrained confrontation.
As Chancellor Helmut Kohl opens the fourth era in West German history, he inherits foreign and domestic policies that he will not significantly change. He will be trimming social welfare in a period of recession. He will be consolidating West Germany's role as a medium power in the heart of Europe.
More than anything else, however, he may turn out to symbolize normality - the humdrum shift of power in a democracy that now requires an alternation of parties only to change the ins and the outs - and not to engineer historic contributions that only one party can give.