One of Turkey's leading politicians warned Sunday that a political vacuum could cripple the domestic battle to keep Islamists at bay and the fight abroad for the extradition of a Kurdish rebel leader. No party has a majority to govern alone in the deeply divided parliament. The head of Turkey's pro-Islamic party said Thursday he would not insist on his rightful chance to lead Turkey's next government, heading off a confrontation with the military that would only deepen the nation's political crisis.