LET’S go now to the latest Twitter outburst from Donald Trump: an unfounded murder allegation.

As the US Covid death toll passes 100,000, the President has other priorities to attend to, such as insinuating that a TV host he doesn’t like killed a Congressional aide 20 years ago.

The woman had an undiagnosed heart condition and died of natural causes. Everyone, but everyone, has pointed this out. The dead woman’s husband, clearly distressed, has accused Mr Trump of spreading bile and pleaded with Twitter to take down the tweets. But the President doesn’t appear to care.

That’s not all. The President has also found time this week to claim postal voting in November will be “substantially fraudulent” (he thinks it will boost the Democrats). This ridiculous claim was too much even for previously indulgent Twitter, which has slapped Mr Trump’s tweets with “get the facts” warnings, deterring the President not one bit and ensuring that Twitter itself is now in his crosshairs.

Meanwhile, Mr Trump has sneered at his Democratic rival Joe Biden for wearing a face mask and threatened the Governor of North Carolina for not yet green-lighting plans to pack thousands of Republican supporters into an arena in August for the party convention. All this since Monday.

“New low”? If only.

What is most shocking about Mr Trump’s behaviour during this crisis is not his lying nor his self-pity nor his conspiracy theorising – we’re used to all that. It’s not even his bird-brained pronouncements on injecting disinfectant or bigging up the malaria drug hydroxychloroquine, which the World Health Organisation has now banned from coronavirus trials.

It’s his chilling lack of empathy with suffering Americans and his unwillingness to take responsibility for his administration’s failures.

There is widespread anger that lives, perhaps running into the tens of thousands, have been needlessly lost because of the government’s ineffective response.

Not everything is Mr Trump’s fault. The national public health agency, the Centres for Disease Control, failed in February to roll out testing effectively, allowing the virus to take hold.

But Mr Trump has downplayed Covid from the get-go, talking at the end of March about opening the economy by Easter and claiming on March 30 that the virus was “going away” even as numbers rose. As always, his base have taken their cue from him, resulting in armed right-wing demonstrations against lockdown. The President knows that if people are suffering financially by election day, he will likely suffer. He can’t let that happen. Power to him is all.

Boris Johnson is no carbon copy of Mr Trump, but there is no mistaking the parallels. Yes, Mr Johnson is slyly artful, the hollow man playing the affable rogue, while Mr Trump only ever plays his narcissistic self. Mr Johnson is intelligent in his way, Trump frequently incoherent. Mr Johnson at least attempts to effect a statesmanlike tone; Trump is incapable even of that. In this crisis, Johnson has not sought to scapegoat others as Mr Trump has and nor has he embarrassed himself on Twitter.

But both are naked populists. Both are lazy. Both are needy elitists who achieved power on the back of claims to represent the disenfranchised. Both are straw men, unequal to the task of stewarding the ship during a national emergency. Mr Johnson has shown a degree more self-control than Mr Trump but he too has a history of indulging in dog-whistle politics when it suits him. He too wants to press ahead with rebooting the economy and schooling in the face of ongoing concerns about safety. And both have shown more concern for preserving their own power, as we saw this week with Mr Johnson’s defence of Dominic Cummings, than doing right by the public.

Now, as with Mr Trump, we are seeing in Mr Johnson the limitations of a leader whose attachment to public service is weaker than his attachment to “world kingship”. As Mr Johnson floundered this week he fell back, embarrassingly, on the campaign trail techniques of last autumn. Echoing his “get Brexit done” slogan, like a one-trick pony he insisted repeatedly that people wanted to move on from the Cummings episode and would be put off by MPs bickering, as if it were Brexit all over again. But this isn’t Brexit and people are not annoyed with MPs: they are annoyed with the PM.

Just as the transatlantic parallels are hard to miss, so is the north-south contrast. Nicola Sturgeon didn’t just fire an adviser who broke lockdown rules where the Prime Minister did not, she has a command of the detail and a willingness to answer questions about it where Mr Johnson retreats too often into bluster and evasion.

In recent years the world has been swept with a populist wave but populist rhetoric cannot solve a real crisis, as the people of Brazil are discovering: cases are rising sharply there after Jair Bolsonaro refused to take the virus seriously. Populist leaders are finding they cannot hide from their failings during this crisis.

Sitting presidents are usually re-elected but Mr Trump, novelly, faces an incumbency disadvantage after handling Covid so poorly (nearly 60 per cent of Americans disapprove of him). The President believes restarting the economy is his ticket back to the Oval Office, but it could also, plainly, be his last presidential act if it prompts a second wave of Covid as election day approaches.

Joe Biden for his part has one big advantage: not being Donald Trump. He is gaffe-prone, as he reminded Americans this week, suggesting that if black voters didn’t back him then they “ain’t black”. There is an archive of his past speeches currently locked up in a Delaware University archive which could provide a string of embarrassments. But he is ahead in the polls, particularly, crucially, among seniors, whom Hillary Clinton never won over. Democratic divisions are healing, with Bernie Sanders backing Mr Biden and talk of a left-wing woman like Elizabeth Warren as Biden’s running mate. And constructing a post-Covid recovery plan, drawing on his years of government experience, has given heft and shape to Biden’s electoral offer as Mr Trump flounders.

Covid might persist, but we can dream of being Trump-free by Christmas. As for Mr Johnson, six months after his election the populist veneer is coming off and his erstwhile supporters are seeing to their cost what’s underneath.

Our columns are a platform for writers to express their opinions. They do not necessarily represent the views of The Herald.

Read more: Think it’s nearly over? Think again: the real danger is now