A week into President Obama’s campaign to win support for punishing Syria for using chemical weapons, the public has increasingly turned their back on him, according to a new Pew Research Center poll that has to be depressing to the White House.

In a week, the number who oppose Obama’s airstrikes has jumped 15 points, from 48 percent to 63 percent. Just 28 percent support Obama, said Pew.

From the authoritative polling operation today:

Over just the past week, the share of Americans who oppose U.S. airstrikes in Syria has surged 15 points, from 48% to 63%, as many who were undecided about the issue have turned against military action, according to a new national survey from the Pew Research Center and USA TODAY.

By contrast, the share of Americans who support airstrikes remains virtually unchanged: Just 28% favor U.S. military airstrikes against Syria in response to reports that its government used chemical weapons.

The new survey by the Pew Research Center and USA TODAY, conducted Sept. 4-8 among 1,506 adults, finds that this growing opposition to Syrian airstrikes is intense: 45% say they oppose airstrikes very strongly. That is roughly three-times the percentage (16%) that strongly favors airstrikes.

Republicans, in particular, have turned against airstrikes. A week ago, 35% of Republicans favored and 40% opposed military airstrikes. Today, Republicans oppose airstrikes by an overwhelming 70% to 21% margin, with 51% saying they are strongly opposed. Opposition has grown among independents as well, with two-thirds (66%) now opposed, up from half (50%) last weekend.

Democrats continue to oppose military action: 53% oppose airstrikes against Syria while 35% support them; the margin is little changed from a week ago (29% favored, 48% opposed).

Barack Obama’s standing with the public has declined. His overall job approval has slipped into negative territory (44% approve, 49% disapprove) for the first time since early last year. Public ratings of his handling of foreign policy – once an area of relative strength for the president – have slipped and now just 33% approve. And when it comes to Obama’s handling of Syria in particular, more disapprove than approve by nearly two-to-one (56% vs. 29%).

As Obama prepares for his address on Syria on Tuesday, a majority of Americans (54%) say he has not explained clearly why the United States should launch military airstrikes against Syria while 35% say he has. A week ago, 32% said he had explained clearly the reasons for airstrikes and 48% said he had not.

The public, by roughly two-to-one (61% to 30%), believes that Congress – not the president – should have final authority over whether the U.S. conducts airstrikes in Syria.

Although six-in-ten agree that the U.S. must act to show that the use of chemical weapons is unacceptable, just 42% of those who express this view favor U.S. airstrikes against Syria.

A narrow majority of the public (54%) says the U.S. has a moral obligation to stop the violence against civilians. But an even higher percentage (75%) says that U.S. airstrikes in Syria are likely to make things in the Middle East worse. And just 39% say the U.S. will lose credibility around the world if it does not act in Syria.

The public is divided over whether the situation in Syria is a threat to U.S. security: 45% say it is, while 50% say it is not. And about six-in-ten (61%) agree there are no good policy options for the U.S. in how it deals with Syria, while 34% disagree.

For the full survey, go to http://www.people-press.org/2013/09/09/opposition-to-syrian-airstrikes-surges/. This survey is for immediate release and is available at the Pew Research Center website at http://www.pewresearch.org.

Paul Bedard, The Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.