Newly elected Republican senator Thom Tillis said this morning that he supports a new authorization for the use of military force, effectively a declaration of war, against the Islamic State, presumably like the one introduced by Senator Tim Kaine, a Virginia Democrat. His fellow senator-elect Gary Peters, a Democrat from Michigan, agreed.
President Obama had considered proposing such a measure earlier this year but decided that it could wait until after the election, choosing instead just to get authorization for vetting, training, and arming Syrian rebels. Currently, the air strikes and operations against the Islamic State in Iraq and Syria rely on the 2001 and 2002 authorizations of force, which enabled the U.S. to attack al-Qaeda and al-Qaeda-related entities and to wage war in Iraq, respectively. The president has said he would like to repeal and refine those resolutions, but has done little to push for such a vote.
An AUMF would not be simple up or down vote: The measure may have to define what kinds of force are allowed (e.g., allowing or ruling out ground troops) or put a time limit on the authority (Senator Rand Paul has suggested a one-year resolution).