To appreciate what‘s at stake for the world in this year’s US presidential election, it is useful to visit a place like Australia that has been one of our most faithful allies -- and that appears to be mortified at what is happening in American politics.

Australians are polite, in their own rowdy way. And they know they have to live with whoever is elected president. So people here rarely criticize Donald Trump head on.

But polls tell the story: A June survey by the Lowy Institute, a think tank here, found that just 11 percent supported Trump, compared with 77 percent for Hillary Clinton. The percentage supporting Trump’s foreign policy was even smaller.

And most amazingly, in a country that has backed every American military action for a century, 59 percent of Australians say their country shouldn’t join in US military action if Trump is elected.

Australians, like most US allies, depend on a strong, confident America to lead a global system that‘s stable, and also supple enough to accommodate new players such as China. They fear an America that leaves allies to fend for themselves against Russian or Chinese bullying.

So what do Australians think when they hear Trump say, as he did in an Aug. 8 speech: “Americanism, not globalism, will be our new credo”? they worry that he means just what he says. Trump’s America would be a more selfish nation; it would look out more for itself and less for others. This inward focus may make sense to Americans who are unhappy with globalization, but it‘s a scary prospect for an Australia that has to bet its future, quite literally, on America’s staying power in Asia.

"We need confident, competent, outward-looking US leadership. Our region depends on that," Australian Foreign Minister Julie Bishop told me in an interview. While she was careful not to express a political preference, her meaning seemed obvious.

Trump’s fulmination about trade deals is a particularly worrying example of his intention to abandon longstanding American policies. He blasts the Trans-Pacific Partnership, for example, ignoring the fact that the greatest beneficiary of TPP’s demise would be China. Beijing is waiting with its own alternative structure for global trade and economics to replace the US-led system that has prevailed since 1945.

Trump’s supporters may imagine that America will start “winning” again, post-TPP, but I have yet to meet a global business leader who doesn’t think that the demise of the trade deal would be a huge victory for China that would undermine American power in Asia for years. And yes, folks, TPP‘s demise would also hurt American workers by reducing US access to the world’s fastest-growing markets.

Clinton’s capitulation to misguided critics of the TPP has been sad to watch. Maybe she really believes that it’s possible to reopen negotiations and get a better deal, but if so, she’s nearly alone.

More likely, she’s willing for US economic power and prestige to take a hit, if it will help her get elected. The only adult American in the room on this issue has been President Obama, who is campaigning hard to get TPP passed before he leaves office.

"The TPP is not just an economic necessity, it’s a strategic necessity," argues Bishop. “If the TPP fails, it will be seen as a failure of US political will. A failure will also leave a vacuum, which will be filled by other countries including China. It’s absolutely vital to have a win on this.”

What will allies do if the US votes to embrace Trump’s version of “Americanism, not globalism”? They will make adjustments; they will hedge their bets; they will hope that the fever breaks in four years; they will try to protect their own interests in a world where American power has become less reliable.

Australia is a good example of a country that stands by its friends, even when they make mistakes. The leadership here stuck with the US through Vietnam, Iraq and Afghanistan. Some business leaders want cozier relations with China, but the public view is steadfast. “Why would we seek to hasten the drawing-down of an old ally?” asked Michael Fullilove, executive director of the Lowy Institute, in a recent book.

Great powers sometimes crack under strain. Australia watched as the seemingly unshakable power of the British Empire became brittle and weary, and turned inward. Global leadership isn’t a perpetual motion machine. It requires effort and occasional sacrifice. This year is a character test for America, and you need only travel abroad to understand how intently the world is watching.

By David Ignatius

David Ignatius’ email address is davidignatius@washpost.com. -- Ed.

(Washington Post Writers Group)