Fresh from the diplomatic carnage of the G7 summit - well, let’s be honest, the G6 + 1 - Trump has arrived in Singapore to rip up even more convention.
Never before has an American president met with a North Korean leader.
Never before has there been a nuclear summit where one of the principals is so little prepared, and the other is so little understood.
We are entering uncharted diplomatic territory, and even the experts are guessing how this will unfold.
President Trump told reporters before he left that preparation is overrated and that “attitude” is the key to a successful summit.
That didn’t work so well in Canada. But perhaps he is right with regard to North Korea.
Decades of cautious and calibrated US policy has failed.
The regime in Pyongyang has become one of the great global risks: A pariah state with a nuclear arsenal, a long-range missile programme and a maverick leader.
So maybe some spontaneous and unstructured personal diplomacy, however risky, has a greater chance of success.
Whatever you think of Trump - and his band of international supporters is dwindling fast in the aftermath of the G7 summit - the world needs Singapore to be a success.
Or at least not a failure.
A blazing row, or a walk out, or some version of a diplomatic trainwreck, would be a disaster.
That’s because there’s no B-plan for North Korea. There’s either a diplomatic breakthrough or the likelihood of a catastrophic conflict.
America has made clear that it cannot tolerate a rogue regime with a nuke and the means of delivering it.
So to say that a lot is riding on Tuesday is one of the great understatements of the century.
Throw into the mix the president’s wild gyrations on North Korea - from "fire and fury" to warmly hosting a former spy chief in the Oval Office - and you can see why the region will be watching the summit with a mix of disbelief, profound hope, and deep anxiety.
As a candidate, Trump described unpredictability in foreign policy as a strategic asset.
That statement - so provocative to those who practice the art of diplomacy and who value stability - faces the ultimate test at 9am local time on Tuesday on this small, crowded island in the heart of Asia.
Hold your breath.