Rudd, the politician, would have let fly after Trump's attack, which was laced with both insult and threat. Rudd, the ambassador, has to hold his tongue.

It doesn't take much imagination to hear the former prime minister's colorful language behind closed doors.

Trump's gratuitous comments, in an interview with British right-wing ex-politician and now broadcaster Nigel Farage, were typical Trump.

Asked about Rudd, the former president said: "I heard he was a little bit nasty. I hear he's not the brightest bulb. But I don't know much about him. But if, if he's at all hostile, he will not be there long."

The federal opposition, predictably but inappropriately, tried to score a political point. The manager of opposition business, Paul Fletcher, asked Prime Minister Anthony Albanese whether he'd reassess Rudd's position.

This was hypocritical and shortsighted. Hypocritical, because Opposition Leader Peter Dutton was on record praising the job Rudd is doing. Shortsighted, because it is important that Australia's senior diplomats - especially in a post like Washington and a time when the US is divided and chaotic - should have bipartisan support.

George Brandis, the former Liberal attorney-general who also served as high commissioner in London, made the case on Thursday.

He warned that lack of such support diminished the person's authority "and therefore diminishes their influence in the country in which they are accredited". Brandis told the ABC Rudd "has plainly done a very good job in the time since he's been there".

Both sides of politics frequently put former politicians into the US ambassadorship, and they can be particularly effective in the Washington jungle.

In recent years Kim Beazley (former Labor leader), Joe Hockey (former Liberal treasurer) and Arthur Sinodinos (former Liberal minister) have all served Australia extremely well in Washington.

Hockey was able to get an "in" with the Trump camp before he was elected, and used some golf diplomacy to build a relationship with the president himself.

Rudd was a controversial appointment, even within Labor. But his background, both as a former PM and foreign minister and an expert in international relations and notably on China, well qualified him for the post.

He has so far met its key performance indicators, especially in relation to AUKUS . Predictions he'd shoot his mouth off have been off the mark.

How well Rudd would go if there were a Trump administration is unknowable. Not as well as Hockey did probably. But likely well enough; he should have the skills and contacts to work around some of the obstacles he'd face.

The bigger and broader question is how the Albanese government would manage a Trump presidency.

In his book Trump's Australia, published last year, Bruce Wolpe, who was a staffer for Julia Gillard and worked with the US Democrats, wrote: "Australian democracy will survive Trump. But the alliance with America may not. As long as Trump is within reach of the presidency in 2024, this question is a clear and present danger to Australia and its future."

At government and bureaucratic levels, there is what is described as much anxiety about the possibility of a Trump presidency. Views among experts differ about Australian-American relations if that eventuated.

Australian National University strategic expert John Blaxland, who is currently based in Washington, says while the optics of the relationship would be rather different, the substance wouldn't change much.

That substance, Blaxland says, is driven by realpolitik - the crucial, increasing importance of Australian naval facilities for submarine warfare, the intelligence footprint and the large amount of US investment. "America is hugely invested economically in Australia. Trump, if anything, is a businessman."

In addition, he says, "across Congress and in the circle of Trump administration appointees there is a remarkable level of goodwill towards Australia".

Blaxland discounts the Trump sledge against Rudd, saying Trump would only act "if something else happened and that won't happen". Rudd has been "scrupulous" as ambassador; "the idea he's going to lunge at Trump is far-fetched".

Blaxland sees Trump's attack as "designed to give him a leg up in any future negotiations with Australia or Rudd".

Sydney University's Simon Jackman is less sanguine. He believes managing a Trump presidency would be a "challenge" for the Albanese government, as it was for the Coalition government.

Jackman argues that a second Trump administration would be different from his first, when many officials moved in at lower levels to protect American foreign policy and US alliances from the excesses of Trump.

"That won't be in place in Trump Mark Two. Loyalty to Trump will be turned up by a factor of ten."

Operating in Australia's favour, Jackman says, would be two factors in particular. Trump "sees China in broad terms, he gets the totality of China", and Australia is a "paying customer - hard money is changing hands in exchange for access to American military technology".

At a personal level, Jackman believes the Albanese-Trump interactions would be likely confined to the sidelines of international gatherings, rather than the PM being feted in Washington. As for Rudd, Jackman says Australia "might have to rethink" his position, although no doubt a transition would be finessed.

When Albanese contemplates the possibility of a second Trump presidency, he might remember that his two predecessors, Malcolm Turnbull and Scott Morrison, were able to ensure Australia did quite well in protecting its interests (varying from preserving a refugee deal to avoiding punitive action against steel).

For Albanese, it would be a matter of finding his own way of dealing with an extraordinarily unpredictable and difficult leader of our main alliance partner.

Meanwhile the joke in American diplomatic circles is that Trump's sledge pales besides some of what Rudd's colleagues used to say about him.