Mr Donald J. Trump turns 72 on June 14, two days after his summit with North Korean leader Kim Jong Un. The question is, will he pull off the deal of his life as a birthday present to himself?

Mr Trump sees himself as an ultimate dealmaker. "I make deals, that's what I do," he often declares.

He has survived serial bankruptcies, been his own boss, with his name in big gold letters on his own big buildings, and starred in a hit reality TV show, The Apprentice.

He is the consummate salesman, a master manipulator who uses social media to ruthless advantage to bypass legacy media.

His style is to counter-attack. In 2014, he tweeted a quote from film director Alfred Hitchcock: "Revenge is sweet and not fattening."

Much of his controversial rise to the White House was based on his pledges to challenge the status quo.

He poured scorn on the Trans-Pacific Partnership, Paris Agreement on climate change and the long-standing North American Free Trade Agreement (Nafta) - saying the US had been taken advantage of.

He backed out of the first two and may pull out of the third.

Mr Trump sees himself as anti-establishment, and unencumbered by norms - which is partly how he appealed to his disgruntled white blue-collar base.

"Out of the box doesn't even begin to describe him," says Ms Gwenda Blair, who teaches at Columbia University's Graduate School of Journalism and met Mr Trump for her 2000 book on the family titled, The Trumps: Three Generations That Built An Empire.

Underlying his rise is a preoccupation with legitimacy and validation. For decades, snooty Manhattanites saw Mr Trump as an upstart from Queens.

For instance, Mr Trump seemed obsessed with the size of his inauguration crowd. He preens before crowds, talking about himself using hyperbole and superlatives. In speeches, he often brags and boasts, to the distaste of the urban liberal set. But he does so in direct and grating terms, channelling the language of a disaffected middle class left behind by globalism.

"He built a brand based on the idea of the best of the best, super luxury, the best ever, the shiniest, glitziest, most expensive, most wonderful, most luxurious, That's his brand, and this is a brand extension into the White House," says Ms Blair.

"So whatever he does in the White House has to be superlative."

His belligerent approach to negotiating is an example of what experts call distributive bargaining - making outrageous demands and hoping the other side gives ground in a zero-sum situation, Dr Fen Osler Hampson, a distinguished fellow at the Centre for International Governance Innovation in Canada, told the Huffington Post last year.

But many say this has been about tearing up agreements but not constructing anything to replace them.

"As a diplomat, Donald Trump has accomplished nothing positive so far," Dr H. W. Brands, professor of history at the University of Austin in Texas, told The Straits Times.

He cited Mr Trump's "numerous negative accomplishments", including weakening Nafta, the Paris climate accord and the Iran nuclear deal and undermining the confidence of US allies, democratic values and the rule of law.

"His supporters find much of this encouraging, being isolationist by inclination. But most of those who expected more from the US have been dismayed," Dr Brands said.

Mr Trump appears to revel in strategic ambiguity, but he also has clear obsessions, say analysts, including to better his predecessor, Mr Barack Obama. Seldom does a week pass without him or his surrogates comparing his administration favourably against Mr Obama's.

A salesman and a performer, he is "forever looking for the unexpected thing to do that will keep us at the edge of our seats. He has several balls in the air, and North Korea is one of the biggest", Ms Blair said.

Mr Trump is focused on his own near-term political gains in making policy decisions, said Dr Glenn Altschuler, professor of American studies at Cornell.

"However impulsive the decision was to accept Kim Jong Un's offer of a meeting, he has come to understand it is giving him the possibility of a significant boost in his stature," he said.

Both Mr Kim and Mr Trump have an incentive to declare victory following the summit.

But Mr Trump's cancellation of the summit, and his subsequent recommitment after overtures from North Korea, have been to his advantage.

"He can say, 'They came to me, I gave it a shot but I always understood the possibility it would not work out,'" Dr Altschuler said.

"This gives Trump an opportunity to be anointed by his supporters, and accepted, as an international statesman."

In an article in The Globe and Mail in April, Dr Hampson and former Canadian ambassador Derek Burney wrote: "His persistent demeaning of previous administrations is derisive and offensive. And the combination of Mike Pompeo as secretary of state and John Bolton as national security adviser is far from conventional.

"If nothing else, it will reinforce Mr Trump's capacity to keep everyone, allies included, off balance by going against the grain of orthodox diplomacy."

It is hard to ignore any view expressed on global issues by the leader of the world's most potent military force and the largest global economy, they wrote.

"We are just not accustomed to seeing American power asserted in such an undisciplined, undiplomatic fashion...

"But as he turns conventional wisdom on its head, he may actually deliver some global dividends, such as peace on the Korean peninsula."

Dr Brands echoed the thought. "His unconventional style may yet produce positive results," he said. "Stranger things have happened."