Remember when pundits were worried that Americans had turned isolationist? As recently as August, polls showed big majorities opposed to military intervention in Iraq, Syria or anywhere else.
But it only took a couple of beheadings by Islamic State to turn a nation of war-weary noninterventionists into an angry, warlike tribe.
In a CBS News poll last month, a massive 71% of those surveyed said they supported continued air assaults against Islamic State, also known as ISIS. Even more notable, the number of people who supported sending U.S. troops to Iraq "to fight ISIS militants" (which sounds like ground combat, something President Obama has said he won't do) had increased to 47%, up from 39% in September. And a big majority said they believed U.S. ground troops were needed to defeat Islamic State in the field.
There are still a few holdouts, of course. Last week, when the president announced that he was doubling the number of U.S. troops in Iraq, Code Pink protested from the left, and former Rep. Ron Paul (R-Texas) chimed in from the isolationist right.
But in the vast stretch of American politics in between, Obama's decision was broadly accepted on its merits.
On the left, Sen. Bernie Sanders (I-Vt.) affirmed that the militants of Islamic State "have got to be defeated." On the right, hawkish Republicans including Sen. John McCain of Arizona said Obama's escalation was, if anything, too little and too late. Even Sen. Rand Paul (R-Ky.) said the military action was "justified"; his only complaint was that Congress hadn't authorized it.
And that suggests that if the president decides to put some U.S. forces into combat in the fight against Islamic State — now U.S. soldiers act solely as advisors — there is already considerable public support for such a move.
So what happened to all the isolationists?
It turns out that even though the public still yearns for fewer wars and less entanglement overseas, there's at least one big exception: They want a robust response to terrorist attacks against Americans.
"Even when the public wants to withdraw from international engagement, if you hit us, there's a Jacksonian reflex — we're going to protect ourselves," said Andrew Kohut of the Pew Research Center.
And even though Islamic State hasn't mounted any attacks outside its home ground in the Middle East, the group's rhetoric — along with its success in seizing territory and those horrifying videotaped beheadings — quickly convinced Americans that it poses a direct threat to the U.S.
In the CBS poll, 58% said they considered Islamic State a major threat to the security of the United States; 21% said they considered the group a minor threat.
"It's not surprising that people are outraged by beheadings; that's appropriate," said John Mueller of Ohio State, who has long argued that public concern about terrorism has been exaggerated. "But the fact that so may see ISIS as a major threat to the United States frankly amazes me."
Americans have long had a warlike streak. When presidents have made the decision to go to war, even in cases in which the enemy seemed less threatening than Islamic State, the initial public response has traditionally been support — known to scholars as the "rally-'round-the-flag" effect. Such patriotism doesn't always translate into support for the president, however, and it certainly hasn't this time. Even as Obama has escalated U.S. action against Islamic State, his overall standing among voters has remained stuck around the 40% mark.
In the CBS poll, the number who said they believe Obama has a clear plan for dealing with Islamic State actually declined from 35% in September to 29% at the end of last month.
That could be in part a reflection of partisan feeling in the heat of a midterm election campaign. But it also reflects a harsh reality of post-Cold War politics: Presidents don't get as much deference as they used to — even when they're waging war.
"If you go back to the Cold War era, even Jimmy Carter got a big bounce in public support during the Iranian hostage crisis in 1979," Kohut said. "But that was a different time."
Post-Cold War presidents, by contrast, have reaped little or no political gain from going to war — even when they were far more hawkish than Obama.
George W. Bush, Obama's predecessor, was blamed for the early fiascoes of his invasion of Iraq — a taint the popularity of his second term "surge" strategy never erased.
His father, George H.W. Bush, won the Persian Gulf War against Iraq handily — and was turned out of office the following year.
There's no reason to think things have changed. Obama will have to accept the cruel reality of post-Cold War politics: If the war goes badly, his standing will suffer. And even if it goes well, it won't do him much good.