The British Parliament on Thursday voted against the use of force in Syria, dealing Prime Minister David Cameron a significant and unexpected blow

Across the pond, many members of Congress have pressed for a similar vote that would authorize or prevent President Obama from using force following allegations that the Syrian regime used chemical weapons on its people.

On Saturday, they got that opportunity. But could U.S. lawmakers actually vote against authorization -- as their counterparts in the House of Commons did?

The situation remains very fluid -- and we can't emphasize that enough -- but there is plenty of reason to believe that Congress might vote against a use of force resolution in Syria.

For a few reasons:

1. The public isn't clamoring for it: As the Post's Scott Clement wrote this morning, Americans oppose broad military action in Syria 50-42. And even when it comes to limited air strikes using cruise missiles, support only rises to 50 percent, with 44 percent opposed.

The poll also shows just 21 percent think getting involved is in America's national interest, and just 27 percent think it will help improve the situation in Syria. In other words, people view military action as retaliation for Syria's alleged use of chemical weapons more than something that will actually do any good.

If you're a member of Congress looking at those numbers, you don't see much of a mandate for any use of force.

2. War fatigue: The experiences of Iraq and Afghanistan are still fresh in people's minds, and there are enough parallels between those situations and this one to make members skittish.

Already, several members have expressed doubts about the Obama administration's assertion that the Syrian regime used chemical weapons -- something that may not have happened without the weapons of mass destruction controversy in Iraq.

“We are more than mindful of the Iraq experience," Secretary of State John Kerry assured Friday. "We will not repeat that moment.”

Both of these wars were very unpopular in different ways -- Iraq for its case for war and Afghanistan for its length -- and they both make it much harder to sell any kind of military action today.

3. The Iraq war vote: This vote may have cost Hillary Clinton the presidency, and you've got to believe other politicians are wary because of it.

When it comes to politics, it's always easier to vote against something than to vote for it. And if the American people aren't begging you to use military force, you're putting your career on the line by voting for it.

If things don't turn out well or don't improve -- and in a volatile situation like Syria, that's quite possible -- you own it.

4. Bipartisan opposition: Foreign policy and national security are increasingly nonpartisan issues, with libertarian-leaning Republicans and Democrats teaming up against the administration on issues like surveillance.

A similar bipartisan coalition appears to be manifesting itself in this case, with about 70 House Democrats joining about 100 House Republicans in demanding that the administration authorize any use of force.

Obama can't rely on a united Democratic Party and would have to pick off lots of hawkish Republicans (whose ranks are reduced in today's GOP).

This is a difficult case for the Obama administration to make -- both to the American people and to Congress. Kerry's forceful statements on Friday make it abundantly clear that the administration is quite aware of this.