THE atomic bombs detonated over Hiroshima and Nagasaki in 1945 were codenamed “Fat Man” and “Little Boy”.

How painfully prescient that seems at present. In a series of tweets and remarks apparently issued off-the-cuff, the childishly impulsive American president has helped the obese North Korean dictator edge the world closer to a nuclear conflict than it has been in a generation. This weekend, the people of Guam are preparing plans in case of attack.

Threatening “fire and fury” on North Korea, and a military that is “locked and loaded” for action, Donald Trump has ratcheted up pressure, presumably using tactics that work for him in business; or perhaps that’s attributing too much considered thought to the man.

Either way, he is playing a lethally reckless game with an unpredictable foe. Defence secretary James Mattis’s statement late on Thursday that “the tragedy of war” would be “catastrophic” seemed to be aimed at Mr Trump himself.

The president is a liability in the Oval Office – even my cat can see that. The only crumb of comfort is that we’re half a year down, so only three and a half to go, right?

Wrong – not the way things stand, at any rate. No, the really frightening thought is that Mr Trump could easily become a two-term president.

Superficially, the auguries aren’t good: record low approval ratings (at 33 per cent); rumours that the Republican party is contingency planning to replace him before 2020; and heck, the Russia thing. Surely one of the dice has to come up?

But the more he smashes the conventions of statecraft with mendacious, overblown tweets, the more his base loves him. When he asserts opinions based on hunches, he speaks to them. Screeds of anguished text have been written in the liberal press about how Barack Obama voters went over to Mr Trump because they felt alienated by political insiders and “experts” talking down to them; how they mistrust the measured language and political correctness that responsible politicians adhere to. They cried out for an alternative. For all his ineptitude, Mr Trump is that alternative.

And approval ratings you could trip over may not be decisive, with an opposition in disarray. Some polling suggests voters think the Democrats are more out of touch than the Republicans.

Incumbents tend to do well in presidential contests: eight out of 11 administrations since 1945 have won second terms (reflecting a well-documented phenomenon of status quo bias in politics and other fields).

And as for the Russia inquiries, Mr Trump and his team’s smartest (and most cynical) move has been to spend months systematically undermining public trust in the media and the judiciary.

Impeachment efforts would be depicted relentlessly as a witch hunt. The necessary majorities in Congress to remove Mr Trump would be extremely difficult to achieve in any case.

Transcending all of this is the economy and it’s buoyant at present. If it still is in 2020, he can hardly lose. There is no guarantee of that (and talk of war is spooking the markets) but there is time to dip and recover by election time.

The Democrats’ best hope is a candidate charismatic enough to give lukewarm Trump supporters pause for thought. They need a plain-speaking outsider of their own who can make a compassionate liberal pitch, uniting the restive centre left but without alienating working class Americans. And that’s a tall order.

There is one other scenario – that the United States goes to war with North Korea – but that doesn’t bear thinking about.