Former prime minister Malcolm Turnbull has warned a second term as US president for Donald Trump could lead to him being surrounded by more "yes-men" and a shift in US foreign policy.
Trump was recently the first US president to have a criminal conviction recorded, when he was found guilty of 34 counts of falsifying business records.
Speaking to 7.30, Mr Turnbull, who was Australian PM when Trump was first elected to office, said he feared Trump would only be more emboldened should he defeat President Joe Biden in the race for the White House.
"In a second term, Trump will be surrounded by more yes-men and yes-women than ever, and he will feel unassailable, because he will have done the impossible and got himself re-elected," Mr Turnbull said.
He then warned that leaders of nations who were allies with the US would have to stand up to Trump.
"Trump is a bully, with a domineering personality," Mr Turnbull told 7.30.
"And most people's instinct and dealing with him is to suck up to him and be deferential and tell him what he wants to hear.
"Personalities like that surround themselves with people who do tell them what they want to hear.
"If a foreign leader takes the approach of essentially sucking up to Trump and telling him what he wants to hear, then they will just be treated with disdain, and they will get more bullying."
Europe and a 'very different' US
While Mr Turnbull said any Australian PM should stand up for the national interest, doing so could incur the wrath of some political elements at home but in the face of a changing global situation, it would be worthwhile.
One such changing situation is occurring in Europe right now.
French President Emmanuel Macron has just called a snap election after far-right parties achieved big gains at European Parliament elections.
Mr Turnbull said he felt it was concerning and that a second Trump administration would likely do things differently than the US has under Mr Biden.
"It's very concerning because the right-wing parties in Europe that are having some real success are not committed to the values of liberal democracy, as we understand it," Mr Turnbull said.
"And a number of them have very close ties to Vladimir Putin.
'[Some] have opposed the support of Ukraine.
"Viktor Orban in Hungary, even though he's a member of NATO, he went to see Trump at Mar a Lago recently, and emerged triumphantly saying 'when Trump is president, there will not be one more dollar of American aid to Ukraine'.
"So we may be dealing with a very different America under Donald Trump than it is under Joe Biden"
Mr Turnbull himself had an acrimonious relationship with Trump when the pair were leaders of their respective countries.
Mr Turnbull's insistence that Trump honour a deal that the Australian government had done with the US when Barack Obama was president was the source of the problem.
The then-Australian PM had insisted Trump honour the resettlement agreement to America for some people from Nauru and Manus Island.
Trump did not want to honour it but eventually relented, while calling it the "most unpleasant" call he had on a day where he spoke to Japanese leader Shinzo Abe and Putin in 2017.
But if he had his time again, Mr Turnbull told 7.30 he would not change a thing and felt standing up to Trump was the right decision and the reason he earned his respect.
He said he would recommend that any Australian PM do the same while remembering that Trump's "Make America Great Again" mantra is at the core of what he does.
"Donald Trump is particularly transactional," he said.
"You've got to make sure that the point you're pushing with Trump is one that you can say it is in his interest and make him understand that it's in his interest to work with you. "
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