Leaders from both parties expressed confidence Tuesday that the House would support President Obama's request to arm Syrian rebels in the fight against Islamic State militants, an important component of the administration's broader strategy to confront the extremist forces.
But after a day of back-to-back private meetings among lawmakers, the political landscape in advance of Wednesday's expected vote appeared to be shifting, particularly for Democrats whose votes will be needed for passage.
"There's a growing sense that this whole thing is problematic," Rep. Rick Nolan (D-Minn.), who opposes the resolution, said while emerging from an evening session. "This whole thing is evolving rather surprisingly."
Elements of both parties, ranging from liberal Democrats to Republican isolationists, are voicing concerns, including whether opposition fighters will be properly vetted and how to ensure U.S. military equipment doesn't end up in enemy hands.
Anxiety rose after Joint Chiefs of Staff Chairman Martin Dempsey told a Senate panel that he would consider recommending the use of American ground troops if the president's original plan failed. The comment seemed to conflict with the president's insistence that ground troops would not be used in Iraq and Syria.
House Speaker John A. Boehner (R-Ohio) said after a meeting of House Republicans that the president's request for authority to arm the Syrian opposition fighters was "a sound one."
"There's a lot more that we need to be doing, but there's no reason for us not to do what the president asked us to do," he said.
If the resolution clears the House, Senate Majority Leader Harry Reid (D-Nev.) said he expected the measure to pass in the Senate "in a bipartisan vote."
House Minority Whip Steny H. Hoyer (D-Md.) similarly expressed confidence that a majority of the House would vote in favor of the president's request. But he acknowledged that House Democrats raised their concerns during administration briefings Tuesday morning.
"The principal concern is deploying American men and women, spending a large sum of money prosecuting a war," he said. But the action the House is voting on "is limited by time and limited in scope."
Not all members agreed. Speaking on the House floor, Rep. Jim McGovern (D-Mass.) said he would oppose the president's request. He added that Congress had an obligation to draft a new resolution to authorize the president's broader strategy, including airstrikes, rather than focusing on only a narrow component of it.
McGovern sponsored a resolution that overwhelmingly passed the House in July that would require any significant commitment of U.S. forces in Iraq to be first approved by Congress.
"We're talking about war. When you drop bombs on people, that's war," he said. "I know this is a hard vote. But we were not elected to duck the hard votes."
Rep. Jim Himes (D-Conn.), a member of the House Intelligence Committee, said the situation was fluid and it remained unclear whether the resolution would pass.
"I see profound ambivalence about arming Syrian rebels. My sense is that's where the momentum is today," he said.
Dempsey's use of what Himes called "the G word," referring to ground troops, injected further uncertainty. "That's going to change the dynamic a little bit for some people," he said.
Key Democrats downplayed Dempsey's remarks as hypothetical. But several senators said they were still weighing how they would vote.
"I'm very concerned by mission creep and by an open-ended commitment that would conceivably result in Americans having a combat role," said Sen. Richard Blumenthal (D-Conn.). "I want to know more about how that role will be limited, what constraints there will be on the mission of American troops there, and how that recommendation will be made if the chairman of the Joint Chiefs of Staff thinks it's necessary."
Sen. Joe Manchin III (D-W.Va.) will be voting against the measure. "People in West Virginia understand the definition of insanity, and this fits it to a T," he said.
Rep. John Delaney (D-Md.) said that while many of his colleagues had reservations about the options before them, they also understood the need for U.S. action.
"These are both sub-optimal choices," he said. "You cannot just deal with this threat with airstrikes. You need some kind of broader strategy and capability on the ground. And so there's only two options to do that – our troops or someone else's troops."
Efforts to bolster congressional oversight of the training and equipping of Syrians was not enough to sway some lawmakers. Many say they just don't think Obama's proposal will work.
"I think it's a lousy plan," said Rep. Mick Mulvaney (R-S.C.), who will vote against it. "There's a large group of folks who are against it."
"What we're talking about is oversight by Congress of a flawed strategy," said Rep. Mark Meadows (R-N.C.). "I don't like the odds."
White House officials continued to call senators and schedule briefings to bolster support for the resolution.
Still, leaders of both parties remained confident the measure would clear the House and Senate.
"I believe there will be enough votes to pass it," said Sen. John Cornyn of Texas, the Republican whip.
"We need a partner in Syria," said Rep. Adam Smith (D-Wash.), the top Democrat on the Armed Services Committee. "The only way to do that is to start."
The politics of Wednesday's vote were already complicated because the president's request is being taken up as an amendment to a must-pass spending bill. Republicans were likely going to need some Democratic support to ensure its passage. With the Syrian train-and-equip amendment attached, it will likely take a coalition of both parties to send it over to the Senate.
In addition to a classified briefing Tuesday for all members of the House, Democrats had scheduled two separate meetings to discuss the issue internally.
Dempsey's appearance with Defense Secretary Chuck Hagel before the Senate Armed Services Committee was the first of several public hearings on the administration's strategy this week. Secretary of State John F. Kerry will testify before the Senate on Wednesday and the House on Thursday. Homeland Security Secretary Jeh Johnson will appear before the House Homeland Security Committee on Wednesday. And the House Intelligence Committee will have a rare open session Thursday.
Amid the flurry of activity at the Capitol this week – probably the last session for both chambers before the November election – members of Congress are being hosted at the White House on Wednesday evening for the annual congressional picnic.