Like the torrential monsoonal rains of the region, the "great and good" of the world's largest economies are flooding into Da Nang, Vietnam — corporate CEOs, presidents and prime ministers who together command 60 per cent of global economic production worth a cool $US43 trillion.

As they do every year for the APEC Summit, the leaders have rushed into another resort city ferried by their air force jets — with legions of bureaucrats, advisers, security protection and media in tow.

From Donald Trump — making his APEC debut — to the weakest of economies (Papua New Guinea), each leader at the Summit is bound by a universal truth: their status is only as good as their grip on domestic political power at home.

So it is that Malcolm Turnbull enters his third APEC Summit on shakier ground than any other.

In the Philippines in 2015, he basked in the glory of nascent prime ministership.

In Peru last year, he enjoyed the cache that an election victory brings — albeit by the narrowest of margins.

Now, in Da Nang, he represents one of the Asia-Pacific's oldest democracies — and one whose parliament is uniquely at risk of disintegration because of its own constitution.

"Crisis" is the word Mr Turnbull used before boarding his plane, describing the dual-citizenship drama that threatens to cut a swathe through the 45th Parliament.

Alone on the world stage

If they understood it, the other 20 APEC leaders at the Summit table in Da Nang might sympathise with Mr Turnbull, but few could truly appreciate how awkward it is to be an Australian prime minister overseas this week.

None of them rule by a one-seat majority — not even the latest of leaders, New Zealand's Jacinda Ardern.

Many have constitutions they simply rewrite as they wish, by virtue of unfettered one-party rule, and none seem shackled to the original draft of a founding document written more than a century ago.

Seventeen years into the "Asian Century", with China showering billions of dollars across the region and Mr Trump bargaining to extend American hegemony for another decade or so, Australia's Westminster-inherited political and legal traditions seem more a fatal flaw than a bedrock for stable, risk-free investment.

Other regional leaders also cart their domestic political woes with them. ( AP: Andrew Harnik )

'Nothing to see here'

Make no mistake, Mr Turnbull won't be the leader cringing in the corner.

At APEC and then at the East Asia Summit, he'll do his duty as promoter-in-chief of the Australian economy.

New trade deals will be clinched with four economic partners, jobs and growth will be promoted and security ties with the US, Japan, Canada, New Zealand, Singapore, the Philippines and Malaysia will be reaffirmed.

Just don't expect too much of it to capture the headlines.

The Prime Minister is accompanied by an Australian media pack of just over a dozen reporters and camera operators — most of us drawn from the dreaded Canberra Press Gallery — and all attuned to the brutal mathematics of the Parliament on which we report.

Unless Mr Turnbull can 'sell' an enthralling new story of achievement with what's called 'cut through' for the average Australian, it would not betray journalism's trade secrets to forecast what the daily regime of questioning will be:

"What should happen to Member/Senator 'x'?" "How did you so misjudge the High Court ruling?" "Can you rule out an early general election?"

It's a tough place to be for a prime minister abroad in the company of leaders whose gaze is fixed on the greater strategic and economic wins of the century and on the threats to all of it — especially North Korea's unpredictable behaviour.

What happens at home doesn't stay at home

Which is not to say other regional leaders don't cart their domestic political woes with them.

Mr Trump has just cleared the first anniversary of his election win, US pollsters track a dramatic souring of attitudes towards him and Republicans have just suffered heavy swings in gubernatorial elections in New Jersey and Virginia.

Xi Jinping remains embroiled in — but winning — power struggles within the Communist Party.

Even Canada's Justin Trudeau seems to have lost some of the electoral gloss that helped sweep him to office in 2015.

Compared to this, Mr Turnbull would give more than a penny to suffer their political travails at the APEC Summit.

His office had mapped out an ambitious crescendo to 2017 — settling same-sex marriage law, locking in new trade deals, refreshing the ministry and delivering strategic plans for foreign and security policy.

Instead, absent of a clear spirit of bipartisanship, all current indications are that his APEC — Australian Parliamentary Existential Crisis — will be dragged through into 2018.

The Prime Minister should savour the view from this year's summit in Da Nang — he has deep dark valleys to traverse before he makes it to next year's.