Is it permissible for the Imam to lead people in prayer while he is smoking?

One should not pray behind a smoker if someone better is available. However, if no one better is available, or if one prays behind him while he is smoking, the prayer is valid. The majority of scholars hold that praying behind a fasiq (transgressor) is valid, and that whoever prays behind him is not commanded to repeat the prayer, due to the general statement of the Prophet, peace and blessings be upon him: "Pray behind whoever says 'there is no god but Allah'."