The unsettled mood in America right now is in that exquisitely fluid state that presages either a real shift in a country’s affairs or an intense summer storm that will be as severe as it will be short.

The numbers tell you something: a record percentage of Americans believes the country is on the wrong track. The Iraq war remains deeply unpopular. The president is experiencing approval ratings worse than any in modern history and for a longer period of time.

The signs of restlessness are everywhere – from the surprising strength of a fringe antiwar Republican candidate, Ron Paul, to the enduring appeal of a first-term, antiwar senator, Barack Obama, on the left.

If there’s an emerging theme, it is a serious rethink of American intransigence and overreach in global affairs. This is a chastened country. When Gordon Brown comes to visit this week he should take note.

Ordinary Americans are increasingly indifferent to the classic British posture of leveraging US power, money and blood for global stability. They’ve sacrificed enough young soldiers recently for the abstraction of a war on terror. Last week the House of Representatives overwhelmingly passed what was essentially a symbolic motion declaring the intent of the US not to have permanent bases in Iraq.

In a telling squabble among the Democrats, Obama also took last week to accuse Hillary Clinton of being like George Bush and Dick Cheney. The reason? In the YouTube debate last Monday, she had ruled out meeting foreign leaders hostile to the US in her first year in office. Her point: “I don’t want to see the power and prestige of the United States president put at risk by rushing into meetings with the likes of Chavez and Castro and Ahmadinejad.” Her bellicosity earned her sudden and somewhat surprising plaudits from the Republican right.

But Obama, revealingly, didn’t retreat. Sensing an opportunity to score with his party’s base, he counter-punched thus: “The notion that I was somehow going to be inviting [Chavez, Castro and Ahmadinejad] over for tea next week without having initial envoys meet is ridiculous. But the general principle is one that I think Senator Clinton is wrong on, and that is if we are laying out preconditions that prevent us from speaking frankly to these folks, then we are continuing with Bush-Cheney policies.”

Nobody, with the exception of Rudy Giuliani, wishes to continue with Bush-Cheney policies. The question is: what would not continuing with them mean?

Obama is taking a gamble that the bubbling discontent with the foreign policy consensus since the end of the cold war – culminating in the invasion of Iraq – might be creating a space for something new in American politics. On the other side of the aisle, Congressman Ron Paul is making the same bet.

Paul has no hope of winning. But his antiwar, isolationist message has catapulted him from oblivion to fourth place among the Republicans in funds on hand – ahead of John McCain. Both Obama and Paul are internet-driven candidacies, crammed with small donations and hyper-enthusiastic volunteers. They are also representative of a budding and clear revival of what can only be called neo-isolationism. And they have the wind in their sails.

Since the 1930s, isolationism has rarely had a real chance at achieving the kind of ideological dominance it once had in America. The second world war and the cold war – with the fascist and communist threats always in the front of American minds – kept America enmeshed with the wider world. The first Gulf war seemed to presage a new form of engagement – multilateral, order-oriented, pax Americana.

The Bill Clinton years can be seen in retrospect as a kind of neutral zone – with much-reduced military spending, a policy of globalisation and free trade, but with sporadic intervention in various trouble spots: Haiti, Bosnia, Kosovo. Then Bush II – and the launching of the New American Century, galvanised by 9/11.

At first blush, 9/11 seemed to mean the end of even the dream of leaving the rest of the world behind. After all, terror had now reached American soil. War had been declared. What choice did Americans have but to fight back?

But the gruelling, soul-sapping war in Iraq has unsettled that idea considerably. Many Americans look at trying to coax democracy or even stability in the Arab world and conclude that it’s a mug’s game. If this is interventionism, could isolationism be much worse? The lead-up to the war disabused Americans of any notion that they could easily corral global support for their policing the planet. The follow-through has convinced them they cannot do it by themselves either. You can see why opting out has begun to appeal.

The Bush-Cheney argument that we have to fight the terrorists in Iraq or we will have to fight them in Kansas has not persuaded many. And rightly so. The core truth of Islamist terror, as 9/11 proved, is that it’s not that hard for very few people to do a lot of damage. The years-long occupation of a Muslim country, moreover, seems to have made the terror threat worse, not better.

Under those circumstances, why not make a tactical retreat? Almost 65% of Americans say the war was not worth the cost. As the Iraqi parliament prepares to go on vacation, while the sons and daughters of Americans face another hellish August policing a sectarian civil war, the potential for a populist isolationist revival seems real enough.

Can it happen? Practically, it takes a long time to get 160,000 troops safely out of an occupied country. The Pentagon has contingency plans to carry on for another two years. Congress does not seem in a mood to cut off funds. Oil remains a key strategic reason for the US to keep its poker in the Middle East fire. And the Israel lobby may panic at signs of swift disengagement. It’s hard to see a tectonic shift that draws the US away from its late 20th-century unipolar role.

But that doesn’t mean it cannot happen. The logic of the situation as it has emerged these past five years is powerful. The hideous atrocities in the Arab Middle East persuade many conservatives that long-term engagement there isn’t worth the blood of their own children.

Cultural pessimists note that democracy is not built in a few years, or even a generation. American conservatism is not, at its core, a utopian or imperial tradition, and the revival of the antiwar, isolationist right is one of the more striking features of the past two years. On the left, meanwhile, the Vietnam syndrome has never fully dissipated; and oil has become a poisonous excuse for staying in the Arab world.

I see only hints and guesses at this stage. But something is stirring out there – on both the left and the right. Hillary Clinton and the main Republican candidates believe they can outflank it. We’ll find out in these next few months if the discontent has more strength and velocity than they anticipate.

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