The first congressional hearing on President Obama’s request for military force authorization in Syria comes tomorrow when Secretary of State John Kerry, Defense Secretary Chuck Hagel and Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey testify before the Senate Foreign Relations Committee.

The 2:30 p.m. hearing comes nearly a week before lawmakers are supposed to be back in session from the August recess, but many are already back in town to attend administration briefings.

Tuesday’s hearing will be open, but the Foreign Relations Committee holds another hearing Wednesday that will be closed-door.

Kerry will also testify in an open hearing Wednesday before the House Foreign Affairs Committee at noon.

“The president’s proposed military response to the use of chemical weapons by the Syrian regime demands thorough and deliberate congressional consideration,” said chairman Ed Royce (R-Calif.). “This hearing will allow for the administration to publicly make its case and explain its plans to Congress and the American people.”

D.C. Del. Eleanor Holmes Norton (D) said yesterday’s classified briefing hosted by five administration officials was the first bicameral and bipartisan security briefing held since she came to Congress in 1991.

At the briefing lawmakers were shown a classified document, which they could not remove from the room, showing the chain of command demonstrating the likelihood that Assad gave the order to use sarin gas, along with other evidence including the trajectory of the chemical weapon from Assad’s territory to the rebel enclave, testimony from first responders and test results from victims that indicate sarin.

Norton also said they were told Iran and Hezbollah counseled Assad against using the chemical weapons. She added that administration officials couldn’t answer her questions about why Assad decided to use them now.

“Still troubling to me is the U.S. view that a brief strike will have a deterrent effect, presumably on the use of chemical weapons and that Assad, who has tons of chemical weapons, is unlikely to retaliate,” said Norton. “I am also concerned that the U.S. has only a slim coalition – Turkey, France and the U.S. – particularly considering that almost all nations have signed the chemical weapons treaty, including most in the Middle East.”

She added that the administration’s “broad language” in the resolution submitted to Congress on Saturday night “bothered many,” but anticipated changes to be made to the draft during committee markup.

Based on what she heard in the briefing though, Norton stressed that she expects administration pushback to any attempts to narrow the scope of the authorization too much. Officials in the briefing also reminded lawmakers that the president can go ahead without congressional authorization if he chooses to do so.

Both Democratic and Republican leaders have vowed that members will not be whipped to vote a certain way on the authorization.

Yet the veteran delegate said Obama has a long way to go to overcome not just usual partisanship but deep divides on the Syria issue within each caucus.

Norton’s office said she “believes that the president will have to count on the loyalty of Democrats to the president to bring many reluctant Democrats to authorize a strike.”

Rep. Janice Hahn (D-Calif.), one of those reluctant Dems who was urging Obama to come to Congress for authorization, said she took a red-eye flight back from her home state to view the administration’s evidence.

“I do think they have a high level of confidence that chemical weapons were used against their own citizens. One hundred percent whether or not it was Assad who ordered that chemical weapons was not there,” Hahn said on CNN today.

“My big question is, is there another way to hold Assad accountable for this apparent violation of international norms since World War I that chemical weapons are not to be used? So I’d like to know if another way to hold him — another way to send a message besides this seemingly unclear military strike that could lead to much more conflict in the Middle East. How do we know that they’re going to respond by attacking our wonderful ally Israel or will they attack America?” added Hahn, who was on a conference call with Kerry, Hagel and National Security Adviser Susan Rice this morning.

House Foreign Affairs Committee Ranking Member Eliot Engel (D-N.Y.) said he thinks Obama will eventually win the argument.

“I think it’s very early for a lot of people. I think people are skeptical because they’re hearing questions at home and they are surprised that the president decided to come to Congress. I think that when all the facts are known and when legislators in both parties see what is best for the United States, I think that the vote will be overwhelmingly yes. It might be close. I said overwhelmingly, but perhaps not so overwhelmingly,” Engel told CNN.

“But I do think that a majority will vote yes. To vote no would be a catastrophe. And it’s the very first time that many members had evidence presented in front of them. I think they’ve got to study it, digest it and see what happens.”

On the other side of the aisle, House Armed Services Committee Chairman Buck McKeon (R-Calif.) said he “definitely” thinks that coming to Congress for authorization was the right move.

He’s “still open” on how he’ll vote.

“I think that when the president said he shouldn’t cross a red line, he should have put a little more thought into it before he said it. That’s why we’re in this position now. It’s because of his statement and, frankly, I think that this scurrying around trying to reach Congress now is a little bit late. It would have been good to have done this before he ever made the comment across the red line,” McKeon said. “But he’s done it. We are where we are. I think the prestige of the United States is on the line. It’s something that we’re going to have to look at very carefully.”

“But I think that we cannot keep asking the military to perform mission after mission with a sequestration and military cuts hanging over their heads. We have to take care of our own people first.”

House Oversight and Government Reform Committee Chairman Darrell Issa (R-Calif.) said, “To earn my vote of support for limited military intervention, President Obama must present a clear plan focused on effective humanitarian intervention or our national security interests.”

“Tens of thousands have been killed by the Assad regime in this brutal conflict — relatively few by chemical weapons,” Issa added. “A military response that places an arbitrary focus on such weapons will do little to protect civilians and sends a deeply misguided signal that totalitarian regimes should only use conventional weapons to carry out mass murder.”