Tunisian President Moncef Marzouki's secular party is quitting the coalition government in anger at the dominant Islamist party's handling of the country's political crisis. The move by the Congress for the Republic party threatens to deepen the crisis, prompted by the killing of an opposition leader last week. Marzouki was a longtime human rights activist whose ascension to the presidency was seen as a sign of Tunisia's democratic progress after it overthrew a longtime authoritarian president in 2011.