SELDOM IS THE SPOKEN WORD SO electrifying that it reverses a political convention and unhorses the party leader. That is exactly what happened to Germany's Social Democrats last week, however, as they met in Mannheim for their annual congress. Saarland premier and former party standard bearer Oskar Lafontaine delivered such a stem-winder of a speech, rallying the movement to return to its leftist roots, that SPD chairman Rudolf Scharping invited a leadership challenge from Lafontaine for the sake of "clarity." Though under heavy weather of late for presiding over the SPD's plunging popularity and deep malaise, Scharping evidently felt he had no alternative but to give Lafontaine the opening. When the balloting was over, many delegates sat back stunned at the results: 190 votes for the incumbent, 321 for Lafontaine.

Scharping, 48, had a lot to do with his own defeat. Last year he blew a 10-point lead in opinion polls and ended up losing to Chancellor Helmut Kohl's long-ruling center-right coalition in national elections. In the aftermath, key Social Democrats fell out among one another, a turmoil that critics blamed on Scharping's vacillating policies and weak leadership. A rash of resignations by top SPD officials had set the stage for an expected fight in Mannheim over the party's direction. Not in the cards, seemingly, was the chairman's ouster.

Yet as chairman, Lafontaine, 52, is not automatically the SPD's candidate as Chancellor for the 1998 elections. Many voters cannot forgive his opposition to Germany's 1990 unification, after which Kohl soundly defeated him. His stance against sending German troops to help enforce a Bosnian peace may not go down much better, and business is deeply distrustful of what critics termed the SPD's "slide to the left." The party's soul searching seems certain to go on.