Wilfredo Lee/AP Photo

After listening to a classified briefing from five senior administration officials this evening, two more lawmakers came out in opposition to strikes against Syria, one went from undecided to leaning against, while another dozen hardened their positions from "lean against" to opposed.

At this point, even undecided members acknowledge that the vote on authorization stands virtually no chance of passing the House. But it might be a moot point considering the optimism some lawmakers expressed at Russia's proposal that it take over policing responsibilities of the Syrian chemical weapons stockpiles.

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Rep. Darrell Issa, R-Calif., the chairman of the House committee on Oversight and Government Reform, and Rep. Greg Walden, R-Ore., the chairman at the National Republican Congressional Committee, both moved from undecided to opposed tonight.

Issa told reporters he was a "firm no" because "even if the plan succeeded, it would, at best, tell Assad not to use chemical weapons" but "allow him to murder another 100,000."

"I come out of this classified briefing with more questions than when I went in, less answers and more doubt," Issa told reporters. "Many of the questions that were asked by members of both parties, including on the Russian initiative, were not answered satisfactorily."

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Walden declined to tip his hand as he left the briefing, but a short time later issued a statement in which he revealed administration officials "did not persuade me that the United States has a clear or achievable objective in Syria that can only be obtained through military force."

"They have not made the case that dragging America into a civil war in the Middle East is in our national security interests," Walden wrote in the statement. "Absent a direct threat to the United States or our allies and a clear goal and definition of victory, I must oppose using military force in Syria."

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After attending the two-hour briefing, Rep. Ken Calvert, R-Calif., said he is now leaning against authorizing a strike, whereas previously he had been undecided.

"I am more convinced than I was before that President Obama's strategy is unfocused, unrealistic and unsupportable," Calvert said. "Tomorrow, I will listen to our House leadership and the president lay out their thoughts on our possible intervention in Syria. Unless I am presented with some new evidence or compelling argument that convinces me that action is in our national security interest, I simply cannot support the use of our American military in Syria as requested by the president."

Perhaps more troubling for President Obama are the tougher positions of many lawmakers who, until the briefing, had been only leaning against the resolution.

Tonight, Reps. Marsha Blackburn, Charles Boustany, Scott DesJarlais, Tom Graves, Brett Guthrie, Gregg Harper, Sam Johnson, Frank LoBiondo, Blaine Luetkemeyer, Kenny Marchant, Alan Nunnelee and Steve Womack all closed the door on supporting authorization for military force.

"Like in so many other areas of foreign policy, the situation in Syria has been botched from start to finish by this administration," Nunnelee, R-Miss., wrote in a statement. "My 'no' vote is a vote of no confidence in President Obama's leadership."

National Security Advisor Susan Rice, Secretary of State John Kerry, Defense Secretary Chuck Hagel, Chairman of the Joint Chiefs of Staff Martin Dempsey and Director of National Intelligence James Clapper led the briefing. None commented afterwards.