Washington: We think it's June – but October is here already.

US presidential campaigns always brace, with good historic logic, for an event in the last days of campaigning that can be a spanner in the works.

The term was coined in 1972 after Henry Kissinger's "we believe peace [in Vietnam] is at hand" declaration, which is reckoned to have added a couple of points to Richard Nixon's re-election score.

And despite lobbing in mid-September in the 2012 campaign, the sensational audio clip of then GOP nominee Mitt Romney disparaging the 47 per cent of Americans who pay no federal tax helped to finish him and his campaign – and so it was dubbed an October surprise.

In this campaign October is a distant prospect but already we've notched up two dramatic surprises: first, the Orlando massacre, which ought to have been the likely terrorist attack that is seen to favour the Republicans, but which Trump blew off with a response that was conspiratorial, tone deaf and self-centred; and now Britain's stunning Brexit vote – which, again, should be a gift for the anti-establishment and isolationist Trump, but which could bounce badly for both he and his Democratic challenger Hillary Clinton.

The "gift" element for Trump is uncertain because of his undisciplined, schoolboy's early response: visiting Scotland the day the result was revealed, he said he'd be alright, because the value of the pound would fall and he'd make more money at his Trump Turnberry resort.

But Brexit should be the cause of worry and strategic re-engineering in the Clinton campaign, because it is a real-time demonstration of ordinary voters doing as Trump is asking them: ignoring the boffins and responding to their gut instincts in making a momentous and unexpected decision.

Right now Trump is floundering in polls that reflect his fumbled response to Orlando, lagging Clinton by 12 points in the latest Washington Post-ABC News poll; and trailing her by almost seven points in the Real Clear Politics average of national polls.

This is the bounce that Clinton needed on becoming the presumptive nominee – Democrats who voted for her challenger Bernie Sanders are swinging in behind her, at a rate much faster and earlier than her supporters swung to Barack Obama in 2008; and there is no polling evidence - yet - that Democratic voters are shifting to Trump.

It will be a few days, at least, before we see polls for which canvassing was done post-Brexit; and it could be weeks or longer before US voters digest the British vote and/or their response in terms of how it might influence their voting intentions.

The polls that really matter are those in a handful of swing states and out there the race is much tighter – in Colorado, Clinton is ahead of Trump by just one point; in North Carolina by two points; and in Florida by three points. In Wisconsin she's up by a healthier five points.

In Michigan, one of the rust belt states in which some observers predict this election will be won or lost, Democrat congresswoman and Clinton supporter Debbie Dingell sees the Brexit vote as a demonstration of how fed up British voters were – and sees the same attitude in her home state.

"I have been stunned by the number of sane people who have said they know what Donald Trump is, they know what he stands for, but they want to shake up the system [by voting for him]," she told The New York Times.

The political landscape is similar in the two countries: inward-looking nationalism as a response to rapid technological change, globalisation and the dominance of financial markets when many are overlooked – getting stagnant wages, if they are lucky to have a job; living in homes with diminished equity; and wondering about the value of the education for which they'll be paying on the never-never for years to come.

Like the Brexit supporters, Trump's are older, non-college educated, non-urban, xenophobic and untrusting of elites and experts. Yet some US observers argue that Americans would not conflate the Brexit, an idea, with Trump, an actual person.

"Were Trump a highly gifted politician, perhaps he could forge an anti-establishment majority that brought cultural conservatives angry about immigration and political correctness together with Bernie Sanders supporters angry about Wall Street and trade," Peter Beinart writes in The Atlantic.

"But he's not … the struggle over Brexit was a struggle between nationalism and internationalism. The struggle between Trump and Clinton is a struggle between different kinds of nationalism. It's less about America's relationship with the world than about who's really an American."

He could be missing the point. Brexit is built on a great sense of voter disenfranchisement – of which there is an abundance in the US, and it is still very debatable how much of it is being picked up in polling.

There is also an argument that the EU is but a part of the post-1945 global order imposed by the US and its allies, and in which the Brexit vote and the Trump campaign amount to demands for a new order of power, economic relationships, borders and ideologies as a counter to dislocation at home and global migration waves.

Just like the US, the British as victors in the world wars were architects of a global order in which today's body of British voters have ceased to feel comfortable – the UN, NATO, the IMF, the World Bank and a bunch of others seem to be in control, not their government.

"The unhappy English have delivered a body blow to the West and to the ideals of international cooperation, liberal order and open societies to which England has in the past contributed so much," the historian Timothy Garton Ash writes in The Guardian.

How different are those sentiments from Trump's reaction to the Brexit vote: "Come November, the American people will have the chance to re-declare their independence.

"Americans will have a chance to vote for trade, immigration and foreign policies that put our citizens first.

"They will have a chance to reject today's rule by the global elite, and to embrace real change that delivers a government of, by and for the people."

Clinton understands that she needs to reposition herself. At the weekend she lashed out at politicians, saying: "Instead of solving problems, Washington is too often making them worse."

But here Clinton has a credibility problem – as a former first lady, senator and secretary of state, she is the quintessential DC insider. In the minds of voters she helped build the international order of which they are so resentful and she voted for the wars that have made America's place in that order more complicated.

The Remain campaign in Britain found itself confronting indifference from Leave voters, who tuned out in the face of wonky warnings about the risk they'd be taking; and who circled the wagons around a Brexit leadership when told they were nutters.

On the hustings, Clinton has to find a way to leapfrog the tedium of her well-intentioned but eye-glazing policy explanations. She can't rely on trying to scare voters about what a Trump presidency would inflict on the nation – and if she's going to continue asking voters, effectively, to vote for the status quo, she'll need to find a lot more of "the vision thing".