As they try to whip up congressional support for air strikes in Syria, President Obama and his allies may be saving their most potent argument for last, at least among fellow Democrats – the contention that failure to win approval would shatter Obama's credibility and ruin his effectiveness.
"At the end of the day, a lot of these Democrats are going to be with the president," a House Democratic aide told Politico, "because the choice is to vote against [the Syria intervention] and turn the president into a lame duck and destroy his credibility, or swallow it and vote for something that you're not wild about. When you're faced with that kind of decision, most of these fence-sitters are going to come aboard."
That's also the assessment of strategists from both major parties who are veterans of past battles where presidencies have seemed to be at stake. They include congressional votes on George W. Bush's war in Iraq and his father George H.W. Bush's Persian Gulf War. When presidents argue forcefully that their effectiveness is in jeopardy, they often get their way, especially among members of their own party who don't want them to become lame ducks.
"I've got to think that, in the end, the Democrats and some Republicans will come down on the side of protecting the presidency," says a former senior White House adviser to a GOP president.
Obama favors the strikes to punish the Syrian government for using chemical weapons last month in an attack that killed hundreds of civilians, including many children. But most Americans oppose the strikes, according to recent polls.
The Democrat-controlled Senate is expected to approve a use-of-force resolution being sought by Obama, probably next week. If a resolution passes there, the Republican-controlled House would follow up with its own vote. And that's where Obama is in big trouble.
A Politico survey found that if the House voted today on a resolution to attack Syria, the measure would fail.
Senior congressional aides predict that, at most, 60 House Republicans would vote for such a resolution, including Speaker John Boehner, R-Ohio, and Majority Leader Eric Cantor, R-Va.
With that minimal level of GOP support, a very high percentage of House Democrats would have to back Obama's position in order for the resolution to pass. But Politico and other sources estimate that a maximum of 130 Democratic "'yes" votes are now likely in the House, putting the resolution short of the 218 needed for passage in the 435-member chamber.
President Obama, Vice President Joe Biden and other key administration officials are expected to intensify their lobbying over the next few days. And Obama is likely to give a prime-time speech soon, urging support for the resolution.
Ken Walsh covers the White House and politics for U.S. News. He writes the daily blog "Ken Walsh's Washington" for usnews.com and "The Presidency" column for the U.S. News Weekly. He is the author of the new book "Prisoners of the White House: The Isolation of America's Presidents and the Crisis of Leadership." Ken Walsh can be reached at firstname.lastname@example.org and on Facebook and Twitter.