We’re used to hearing that each American election is hugely important. But this time, really, it is. Ask anyone in foreign policy establishments either side of the Atlantic.
For some you need to go back to the 19th century to the eve of the US civil war to find an election as significant as this.
US historian Ed Watts, who wrote Mortal Republic: How Rome Fell Into Tyranny, said he saw worrying parallels with America under Donald Trump and the Roman republic as it sank into decline, and was deeply concerned by damage done to US democratic institutions during the Trump presidency.
“This is definitely the most consequential election that we’ve seen since 1860,” he said. “This is an election where I think it’s very easy to imagine scenarios where the peaceful administration of the United States breaks down. And this is very dangerous.
“I think the way Trump has been blurring his willingness to accept democratic outcomes, that suggests that a Trump victory is going to be really damaging to US political institutions.
“I don’t think it’s going to look like a republic of laws. I think it’s going to look instead like a republic of power where individuals who have power do more or less what they want without significant constraints and that’s a significant danger.”
Others draw a line back almost a century, to the 1930s.
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“I think it’s the most important election since 1932,” said Martin Wolf, chief economics commentator for the Financial Times. “When Franklin Delano Roosevelt was elected at the trough of the great depression and proceeded to change America and the world and proceeded to take America into the world as a great power.”
America led efforts to build the post war world order, a system of democratic and international institutions designed to keep the world prosperous and safe.
Donald Trump is an America first unilateralist and appears to have little time for those institutions.
He has pulled America out of some of them, gone back on America’s word on key international agreements on Iran and the climate, and openly admired strongmen and dictators while at times deriding America’s traditional democratic allies.
“It’s remarkable that Trump admires and respects autocrats like Xi and Putin over Merkel,” said Mr Wolf. “All other American presidents recognised who was on their side.
“We have relied on America. We have lived in the world that America has created. We have prospered in the world that America has created.
“If America pulls out of it, then Britain, particularly outside Europe, will be really on its own in a way it hasn’t been since the 20s and it’s much less powerful than it was then.”
It is not hyperbolic to argue that a Mr Trump re-election could spell the end of the liberal democratic post-war world order.
It would re-confirm that Americans no longer support the institutions and rules that America put in place after the Second World War.
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If that world order falls apart it will be exponentially harder for the world to solve problems threatening us all.
We are still waiting for an international COVID-19 action plan.
Under Donald Trump, America has pulled out of the World Health Organisation (WHO) and not come up with a plan to replace it.
International efforts to save the planet have been jeopardised by his decision to walk away from the Paris Agreement on climate change.
Environmental lawyer Farhana Yamin said the choice between the two presidential candidates could not be clearer.
“It’s chalk and cheese between these two candidates,” she said. “You’ve got a climate deal wrecker Trump who’s tried to kill the climate change agreement and is a fossil fuel champion and a climate denier.
“And you’ve got Joe Biden, who is a champion of climate action at the moment and so the stakes couldn’t be any higher on whether the world moves backwards essentially or whether we move forward.”
This election is a stark choice between a multilateralist who believes America’s problems and the world’s are best solved working with allies, and a committed “America first” unilateralist.
Former Trump campaign official Bryan Lanza is among the president’s supporters who say he has done it his way and it has paid off.
“When you point to North Korea not having the nuclear weapon that we thought they were going to have today or you point to the caliphate being defeated that’s a good thing,” he said.
“When you point to US troops coming out of these countries where they’ve been for 20 years I think you can look at the totality of that policy and can say they’ve hit a good stride, they’ve hit a good benchmark.”
Donald Trump’s critics are dismissive of such claims and fear another four years of the Trump presidency could terminally damage the western alliance.
Sir Peter Westmacott was British ambassador to the US during the Obama-Biden years. He said: “I do think that there’s a real threat to NATO and I do think that some of the international institutions that Donald Trump doesn’t like will be weakened.
“I hope that that doesn’t mean to say that that’s the end of the post-war international order. That would be pretty catastrophic and that would hand game set and match to some of the big malevolent players out there.”
Mr Trump is not the favourite of course. Joe Biden would be a very different president. A confirmed multilateralist, he has promised to restore America’s credibility among allies.
“I think that can be rebuilt and it can be reconstructed,” Sir Peter told Sky News. “And I do believe that a president Biden is going to be very keen to restore values and respect for America as well as putting in policies in America’s interest.”
Others are not so sure. They wonder if the damage has been done, regardless of the outcome of this election.
Karin von Hipel, from the Royal United Services Institute, wonders whether the Trump genie is now out of the bottle.
She said: “Many countries may not trust America anymore.
“They may say well look you elected someone like Donald Trump before. You may do it again and who’s to say that the next version, the next iteration won’t be more competent.”
If that is the case this election may not be so consequential after all.
Regardless of who wins this election, Mr Trump has shown what can be done within the US system of government and could be the trailblazer for others like him.
America will never been seen as quite the same again.