CAN we ever go back? Democratic Party strategists in the United States must be asking themselves that question every day. Entrusted by their supporters with finding a candidate to take down Donald Trump at the 2020 presidential election, the critical judgment for them is this: do they choose a diplomat or a disrupter?

The answer might seem obvious after the president’s jaw-dropping press conference with Vladimir Putin this week, which even many Republicans appear to have watched from behind the sofa.

The raging bull president left them feeling humiliated. All the usual hallmarks were there: his thin-skinned obsession with his legitimacy as president; attacks on the media, Democrats and the special counsel investigating his campaign; the sledgehammer rhetoric.

But what made American blood run cold was the president’s apparently casual disregard for the principle – one nobody thought needed spelling out – that a US president will stand up for American values; that he will defend the democratic process when it is under attack from a foreign foe. Instead, asked about Russian interference in the 2016 election, President Trump sided with the Russians.

It was “the most serious mistake of his presidency”, said Newt Gingrich, usually a Trump supporter. “Treasonous,” said former CIA director John Brennan. The President was “abasing” himself, said Republican elder statesman John McCain, adding icily that Mr Trump was “naïve”.

Perhaps that was the most damaging impression of all. It was like watching a hornet caught in the web of a black widow spider. All Mr Putin had to do was wait quietly while his unwary guest thrashed around, getting more and more hopelessly entangled in a pro-Russian narrative that Mr Putin could have scripted himself (and as good as did).

Where the former KGB agent comported himself with steely dignity, an ingratiating Mr Trump rambled on, stumbling over diplomatic shibboleths and sending them crashing to the floor with one outburst after another. Austin Powers cosying up to Ernst Blofeld could scarcely have been as mortifying.

The sense of a man out of his depth was not diminished when he later tried to withdraw his comments, claiming he had mixed up “would” and “wouldn’t” (and people say Theresa May is embarrassing).

Surely after this impulsive Twitter president, Americans will crave a leader with Ronald Reagan’s mildness and self-deprecation, Bill Clinton’s forensic mind and easy charm, and Barack Obama’s restrained, cerebral language – a return, in other words, to the artfully packaged, carefully calibrated statecraft of previous decades.

But I’m not so sure. Mr Trump has clocked up gaffes and u-turns aplenty; he may already have sown the seeds of his downfall. But when he leaves the White House, he will have H-bombed so many conventions that it will be impossible simply to go back to the old ways.

And that’s not only because the world has become addicted to the sheer horrifying spectacle Mr Trump provides, though his presidency is undeniably riveting, like a Netflix series, House of Blowhards, or a movie franchise, National Lampoon’s Administration. Polling has yet to reveal what the punch-drunk American people make of the latest instalment – Donald Does Europe: Seven Days, Four Countries! – but up until now, he has kept his base on side even when appalled senior Republicans have called him out.

That’s because, no matter how simplistic or poorly briefed he is, no matter how base his motivations – and unfortunately for some voters, precisely because of it – his barrage of unfiltered opinions, delivered not through skilled spokespeople but through Twitter, continue to cut through to Americans.

Mr Trump does not speak in subtleties that have to be interpreted by reporters, which has been the method of presidents for decades, particularly in dealings with foreign leaders. A local government quarterly report on buildings maintenance has more pizzazz than your average post-summit communiqué. They are typically wrung dry of emotion, all colour expunged, until all that is left are shades of grey – this for the very good reason that slight nuances can spook markets and set dangerous political hares running.

But not with Donald Trump. At his worst, he derides foreign leaders at press conferences and airs his grudges on Twitter in a way many of us would hesitate to do in a Whatsapp group with our closest friends. But he does not talk down to voters. If nothing else, many American voters still appreciate that. When he lashes out, it confirms to them that he is human, not some member of that alien political class, the much-derided “elite”.

And so future presidents cannot revert to type. Voters have lost patience with candidates whose public utterances seem rehearsed, who, as they see it, deign to speak to voters only through the priest-caste of reporters who are part of the Washington milieu. In the wake of this disorderly reformation, voters want a direct relationship with their president.

But if Mr Trump has partially recast the presidency in his own image, he has also shown Americans why some of the old ways are still effective. Now that the Oval Office is occupied by a morally vacuous man who thinks it acceptable to tear migrant children away from their parents, it has become clear that his predecessors avoided soundbite policies for an honourable reason. Now that there is a president who acts impulsively on the world stage, it is clear why precision and self-control are valuable to effective diplomacy. Now that there is a president who seeks to undermine democratic institutions that stand in his way, it shows voters how important it is to heed the ethical due diligence on presidential candidates.

So what’s needed, post-Trump, is a diplomatic disrupter. That means a candidate who has the chutzpah to be blunt if the circumstances allow – someone who can detonate a few controlled explosions on Twitter – but who reads her briefing notes first; someone who comes from outwith the political class, but respects the experience of those inside it; someone who can communicate simple policy ideas in public but never without a sophisticated strategy to deliver them.

The old ways? They aren’t so bad.