News of the possible collapse of sexual assault charges against Dominique Strauss-Kahn stunned and divided France on Friday, underscoring political differences between left and right, challenging moral assumptions and spurring supporters to urge his rehabilitation after what had been depicted as disgrace. This is like a thunderbolt, said Lionel Jospin, a former Socialist prime minister who is close to Mr. Strauss-Kahn, the former head of the International Monetary Fund, once regarded as the likely Socialist Party candidate to challenge President Nicolas Sarkozy in next years elections.