Donald Trump's jawboning style and "bullying by tweet" gets results. Just look back at the past six months:

• North Korea back to the negotiating table. Yet when Trump was in full flight — "Why would Kim Jong-un insult me by calling me "old" when I would NEVER call him "short and fat?" — and attacking the "rocket man", there was nervousness aplenty that his goading had brought the world to the brink of war.
• Chinese President Xi Jinping has made useful concessions to the United States on trade. The war between these two elephants of global trade is not over (both sides have yet to withdraw their threatened tariff hikes) but there is finally movement by China on some fundamental issues of importance to American high tech companies.
• Isis has been defeated on Trump's watch. But the war against the caliphate is not entirely over and may be inflamed if the US pulls out of Syria.
• The Trump tax cuts are expected to give a kicker to US economic growth and jobs are up.

These observations are not an invitation to another round of Trump derangement syndrome.

That's the one where sensible people burst into vicious social media attacks against anyone who authors a dispassionate report on, say, the Administration's taxation changes, which is not prefaced by a swingeing attack on Trump's personality or the real reason he is doing battle with Robert Mueller.

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But it is notable just how much the "Political Disruptor-in-Chief" has succeeded in resetting the dial in Washington in the less than 16 months since he was sworn in as President.

Yesterday, Trump proposed re-joining the Trans-Pacific Partnership (TPP) which he had criticised as a "disaster" during the presidential election campaign.

This is a defensive move to ensure US farmers and retailers gain further access to the markets of the 11 TPP partners in case China delivers on a raft of tariff threats against the United States.

It is also intended to boost US influence in the Asia-Pacific region where China is steadily building its power.

But Trump will find the trade game has moved on.

The 11 remaining TPP partners — Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam — late last year forged what is now called the Comprehensive and Progressive TPP (CPTPP) after the United States withdrew. It will be no easy feat for the US to just rock up and say "let us in".

The CPTPP agreement has been signed by the 11 partners. At least six of the accord's signatories must ratify the agreement so it can come into force.

Once that threshold is met the agreement will take effect (for that group) 60 days after they have notified New Zealand, which is the official depository for the deal.

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Trump has asked his advisers to explore joining the CPTPP. But new members can join only as long as existing parties agree.

Trade Minister David Parker says there has so far not been any official notification to New Zealand that the US wants to explore entry.

Trump's potential move on TPP may defuse what looked like an inexorable move towards another inflexion point in the relationship between New Zealand and the United States.

New Zealand has high expectations of the US; Cabinet Ministers and senior officials pull their punches.

But there has been deep concern over the disruption to the international rules-based order of which the US was a major author.

Protectionism — having to choose (or not) between the US or China when it comes to a potential trade war — is clearly one of the issues that is of deep concern to the Ardern Government, diplomats, NZ farmers and businesses.

In last year's annual Herald Mood of the Boardroom survey, chief executives isolated the "Trump factor" as one of the major issues impacting their confidence in the global economy.

They saw the Trump presidency and its resultant political instability as taking the edge off a generally positive outlook. The CEOs rated the "Trump factor" their second highest international concern at 6.47/10.

Specific concerns included Trump's call for an "America first" trade policy with a focus on bilateral trade deals, threats of a nuclear strike on North Korea, and the US withdrawal from the Paris climate accord.

It would be ironic if the upcoming mid-term elections in the US exposed the Democrats as currently more protectionist when it comes to TPP than a President who can change his mind.

New Zealand should welcome a change of heart. But be in no hurry to seal a deal.

Trump might just change his mind again.