Facing the possibility that President Obama might not win a second term, his administration accelerated work in the weeks before the election to develop explicit rules for the targeted killing of terrorists by unmanned drones, so that a new president would inherit clear standards and procedures, according to two administration officials.

The matter may have lost some urgency after Nov. 6. But with more than 300 drone strikes and some 2,500 people killed by the Central Intelligence Agency and the military since Mr. Obama first took office, the administration is still pushing to make the rules formal and resolve internal uncertainty and disagreement about exactly when lethal action is justified.

Mr. Obama and his advisers are still debating whether remote-control killing should be a measure of last resort against imminent threats to the United States, or a more flexible tool, available to help allied governments attack their enemies or to prevent militants from controlling territory.