PRESIDENT Barack Obama has signed up power brokers in Congress for strikes on Syria but, in an era of insurgent politics haunted by Iraq, there is no guarantee the rank and file will follow.
Obama, who is on the road in Sweden, mobilised his big political and military guns on Wednesday to convince lawmakers to back his plan to punish President Bashar al-Assad over a chemical weapons attack.
The White House can already boast two significant victories.
On Tuesday, Republican House Speaker John Boehner and majority leader Eric Cantor, who more normally torment the president, gave robust support to his strategy.
Then, on Wednesday, the Senate Foreign Relations committee voted by 10 members to seven to authorise action in Syria - albeit under tighter rules of engagement than the White House had requested.
"None of us want the US mired down in another conflict, so the committee has significantly limited the president's original authorisation, while still providing for an appropriate use of force in response to Assad's use of chemical weapons," said Republican Senator Bob Corker.
But for Obama to collect on the huge gamble he made in seeking congressional backing for attacks in Syria, he must win over lower ranking lawmakers who, unlike their leaders, are more concerned with their political skins than US standing in the world.
War weariness stalks America, and votes to authorise action in Syria, likely to begin next week, are tough ones - especially for House and Senate lawmakers up for re-election in 2014.
Republicans face a strain of isolationist and libertarian sentiment roiling a party still working through the political trauma of the Iraq war.
Many establishment Republicans have already been knocked off their perches by "Tea Party" candidates who have challenged them from their right in nominating contests.
Anti-war liberal Democrats meanwhile are making unlikely common cause with conservatives like Senator Rand Paul, who oppose US military action.
Hawks like Republican senators Lindsey Graham and John McCain meanwhile demand a more robust effort than the "limited" strikes Obama has proposed and want to escalate US military aid to the Syrian opposition.
This splintering of party lines is complicating efforts to build a coalition behind action in Syria.
But one White House official predicted sufficient support would emerge between the extremes.
National Security Advisor Susan Rice told NBC News she was "quite confident" that the administration would prevail.
Another official admitted privately that the White House "will lose some Democrats" meaning that significant numbers of Republicans will be needed not just in the House, but in the Democratic-run Senate to get the bill through.
Reliable vote counts are not yet available, as hearings on the authorisation, featuring a passionate Secretary of State John Kerry take place on Capitol Hill.
But a top House Democrat, Chris Van Hollen, when asked by CNN Wednesday whether a war resolution could get through the chamber, replied: "I don't think anybody knows right now."
Though Boehner and Cantor are in favour - other top Republicans are wavering and could siphon away yes votes.
The White House has good reason for concern.
Close Obama aides privately vent frustration that Boehner has been unable to deliver his riotous caucus on other big issues, including on proposed budget deals.
Obama, often criticised for a failure to engage on key priorities on Capitol Hill, has been unusually active.
A senior official said the president was calling lawmakers from abroad. On Wednesday, he also hardened his rhetoric.
"My credibility is not on the line, the international community's credibility is on the line and America and Congress's credibility is on the line," he said.
The comments appeared to be a bid to give Republicans, many of whom defy him on principle, a reason to vote 'yes' other than the fact the president's prestige is at stake.
