The biggest question surrounding President Obama's request for Congress to authorize military force against Islamic State is how far his party will back him in the fight.
After the White House sent the proposal to Congress on Feb. 11, Republicans lined up to denounce the resolution as too weak. Some said it should be rewritten to sanction a broader attack, possibly including the use of U.S. ground troops, to destroy the militant group that now controls much of Iraq and Syria.
But some Democrats were equally ardent in their criticism, calling the White House proposal too broad in scope partly because it could allow the Pentagon to expand the campaign of airstrikes against Islamic State, also known as ISIL and ISIS, into other countries.
"I think I speak for Democrats: We want to fight ISIL," Sen. Robert Menendez (D-N.J.), ranking member on the Foreign Relations Committee, said at a hearing Wednesday. "But we can't provide a blank check to this or a future president."
The hearing, which included testimony from retired Marine Gen. John Allen, special envoy for the American-led coalition against the Sunni Muslim extremists, was the first in a series expected in Congress as lawmakers debate and almost certainly revise the president's proposal.
The White House has indicated Obama is willing to change the language. The president wants to show the world broad, bipartisan support in Congress for America's latest military action in the Middle East.
Obama announced the U.S. intervention in August after the militants swept out of Syria and overran western Iraq so quickly they reached the edge of Baghdad before they were stopped.
Since then, coalition warplanes have dropped more than 8,200 bombs on Islamic State targets, and U.S. commanders insist the militants have been put on the defensive.
The fighting in Iraq is expected to grow more intense this spring as Iraqi security forces, Kurdish peshmerga fighters and Shiite Muslim militias try to wrest back several major cities, including Tikrit and Mosul, from the militants.
At the same time, militants claiming allegiance to Islamic State have carried out deadly attacks in France, Libya, Egypt and elsewhere as the group's influence has spread.
Pentagon officials have said they may need to deploy U.S. special forces as ground spotters to help direct fire and guide U.S. airstrikes in the Mosul offensive.
The president's proposal, which would expire in three years, does not limit the missions Obama or his successor could approve, barring only what it calls "enduring offensive ground combat operations."
During his testimony, Allen was pressed to define "enduring." He said it might mean "two weeks," but it might also mean "two years."
Sen. Barbara Boxer (D-Calif.), who expressed regret in the past for not doing more to rally opposition to the Iraq war, made her discomfort clear.
"Democrats have been searching for this definition of 'enduring,'" she said. "I think what you've proven here with your honesty is there is none.... We're very uncomfortable with this language."
In an interview, Boxer said she supports the president's strategy, but not his proposed resolution to authorize military force.
"I'm going to fight very hard against this," she said. "And to be honest, I don't really see the votes for this."
Many Democrats in Congress were elected in the 2006 and 2008 waves by voters uneasy with the Iraq war. Some of these lawmakers are reluctant to approve another open-ended conflict.
When Obama asked Congress in September to approve a narrow component of his strategy against Islamic State, training and equipping Syrian opposition fighters, House Democrats voted only 114 to 85 to support it, for example.
Republicans have made no secret of their opposition to Obama's proposal. Rep. Adam Kinzinger (R-Ill.) introduced an alternative proposal two days after the president sent his to Congress.
"War strategy requires flexibility, and Congress should not tie this and future presidents' hands at a time when the ISIS threat is growing even more powerful and dangerous," he said at the time.
The White House contends Obama can wage war against Islamic State under a resolution Congress approved in 2001 authorizing use of force against Al Qaeda, which once had ties to Islamic State. The president's proposal would rescind the 2002 resolution that authorized the U.S.-led invasion of Iraq, a vote that became a political albatross for many members of Congress.
Administration officials say that the current proposal doesn't expand Obama's authority to send ground troops but that it would force the GOP-led Congress to share responsibility for another war in the Middle East.
Aides say it's far from certain that the hyper-partisan Congress will agree on a new resolution. The challenge for the White House will be addressing Democratic concerns without risking Republican support.
"Whenever you try to resolve the concerns of those of us who are worried about excessively broad authority, the harder it is to get the support of those who apparently want to give the executive a totally blank check," Rep. Chris Van Hollen (D-Md.) said.