WASHINGTON, Sept 2 (Reuters) – After putting a decision to launch military strikes on Syria into the hands of Congress, President Barack Obama is doing what his critics have long accused him of failing to do: reaching out, personally and aggressively, to lawmakers on Capitol Hill.

While top lieutenants including Vice President Joe Biden and Secretary of State John Kerry lobby their former congressional colleagues, Obama is making individual calls himself to members of the U.S. Senate and House of Representatives to press his case for action.

What Obama has not done since he made his announcement Friday is appeal to the public, which both Democrats and Republicans say will be crucial as polls show little enthusiasm for U.S. military action anywhere.

The stakes for the president are high – and the arguments being made in support of a ‘yes’ vote from Congress are making them even higher.

A vote against strikes to punish Syrian President Bashar al-Assad for alleged use of chemical weapons, officials argue, could undermine Obama’s standing in the Middle East as his administration seeks to deter Iran from obtaining nuclear weapons, broker peace between Israelis and Palestinians and stabilize a region already in turmoil.

“A rejection of this resolution would be catastrophic, not just for him but for the institution of the presidency and the credibility of the United States,” Senator John McCain said after meeting with Obama at the White House on Monday.

Mindful of those stakes, the White House has employed a “flood the zone” strategy, according to an administration official, using an American football term for an offensive move where players flood an area of the field to overwhelm the opposing team’s defenders.

The evidence of that strategy: an onslaught of briefings, calls and meetings with lawmakers from both political parties.

On Monday National Security adviser Susan Rice, Kerry, Director of National Intelligence James Clapper and the top U.S. military officer, Martin Dempsey, held an unclassified briefing call for Democratic House members, and Obama met with McCain and fellow Republican Senator Lindsey Graham.

On Tuesday Obama will meet with the chairs of key national security committees in Congress and Kerry, Dempsey, and Secretary of Defense Chuck Hagel will testify to the Senate foreign relations committee.

“In all calls and briefings, we will be making the same fundamental case: The failure to take action against Assad unravels the deterrent impact of the international norm against chemical weapons use,” a senior administration official said.

“It risks emboldening Assad and his key allies – Hezbollah and Iran – who will see that there are no consequences for such a flagrant violation of an international norm. Anyone who is concerned about Iran and its efforts in the region should support this action,” he said.

CONSULTATION, AFTER THE FACT

Obama has stepped up his interactions with lawmakers this year, holding dinners and building relationships that critics say he lacked.

But any goodwill he has obtained from that effort is limited, and one Republican aide noted on Monday that Obama had only come to Congress after already articulating a decision that strikes were necessary.

“They’re certainly doing more, but it’s after the fact. They already made a decision on what they want to do,” a senior Senate Republican aide told Reuters.

Running parallel to the White House contacts with Congress are conversations that senior Democratic and Republican senators are holding in an attempt to get a resolution passed in the full Senate.

The aide said the Democratic chairmen of relevant Senate committees were consulting with the highest-ranking Republicans on those panels to try to work out language that could pass the Senate next week.

Passage in the Republican-controlled House remains much more problematic, with lawmakers expressing skepticism about U.S. involvement in another war as well as the effectiveness of the limited strikes that Obama has proposed.

(Additional reporting by Steve Holland; Editing by Fred Barbash and Cynthia Osterman)