Leaders like Volodymyr Zelenskyy are hard to come by. Are we looking in the right places?

Marvell was capable of better than that. After all, he once admonished a reluctant lover by reminding her that, "had we but world enough and time/Thy coyness, lady, were no crime". For his part, Cromwell might have preferred less flowery fawning. His habit of plain speaking led him to dismiss the Rump Parliament as "a pack of mercenary wretches", distinguished by "contempt for all virtue". "In the name of God, go."

Nonetheless, "if these the times, then this must be the man" captures an essential truth about political leadership. We keep on convincing ourselves, because we need to, that leaders can rise to an occasion, seize an opportunity and surmount a crisis. The finest illustration of that capability, Volodymyr Zelenskyy is respected and admired around the world for many estimable reasons, but also for one silly one.

In other democracies, we are waiting and hoping for someone faintly like him. That folly uses Zelenskyy to project our own wishful thinking. Deep in an election campaign, we try to find a political litmus test, a marker which will help us determine whether a political leader is worthy of our trust. We make a mistake when we assess putative leaders on the basis of moral criteria rather than working out how much they can learn, how hard they will work, how well they consult and how readily they admit and correct mistakes. Taking a joke also matters.

Why look for vision, when the two best leaders of this country, Curtin and Chifley, were, as Paul Keating cruelly remarked, a "trier" and a "plodder"? After all, one of the most successful political visions of our time, Francois Mitterrand's "la force tranquille" ("quiet, calm strength", now plagiarised by Emmanuel Macron) was unintelligible guff?

Why rely on shows of old-fashioned probity? Although no politician now dares to behave as grossly, and boorishly as the younger Bob Hawke, Boris Johnson may suit our benighted contemporary mores more than did Angela Merkel.

Why turn to eloquence, a skill devalued by Barack Obama, who failed to persuade those of contrary views to drive change with him? Eloquence can leave a bitter aftertaste of hypocrisy and grandiosity. Not even Jacinda Ardern, who can infuse eloquence with empathy, can transform a moving speech into material progress.

As for faith, electorates have rightly become sceptical of leaders who claim divine blessing or inspiration. When any politician, like Tony Blair or George W. Bush, talks about his religion, he surely debases a private, personal conviction in the service of electoral gain.

Finding a rational basis for many decisions is beyond us. I remember selecting a nanny from Ireland when we lived in Paris, depending on one telephone conversation alone, then struggling to find ways to ask her politely if she was an axe murderer. When appraising politicians, we might go in search of an ordinary man, reminding ourselves of Abraham Lincoln's judgment that the Lord must love ordinary folk, because he made so many of us.

In the absence of credible Zelenskyy look-alikes, our best current guide may be a new biography of Harry Truman, US president from 1945 to 1953 (The Trials of Harry S. Truman by Jeffrey Frank. Simon and Schuster). Here we have a mediocre fabulist, "a little man in a big job", a failed haberdasher long in thrall to a vicious party machine (the Pendergast gang in Missouri).

Truman was "rarely introspective or reflective", fond of a game of poker and a glass of bourbon, who indulged in "jump decisions" (quick, intuitive but rash ones). He wrote scathing letters to his political enemies, then hid them away in his desk drawer. Nixon's enemies list was rather more orderly.

Truman literally had greatness thrust upon him. The former timekeeper and mail clerk, re-elected to the Senate with tainted votes, became president after a few months as a scorned, ignored understudy to a dying man. Remarkably he survived and went on to win re-election in 1948, delivering one speech each working hour at every whistle-stop in the land.

Yet the scale of his achievements comes more sharply into focus as the years go by. Seventy-four years ago Truman described himself as a typical farm product, the epitome of "the completely unterrified form of American democracy". What an extraordinary adjective he chose; "unterrified" connoted determination and grit, both "concealed behind a mask of down-home forthrightness and folksy language".

With all those blemishes, to each of which Truman readily admitted, the state of Israel was recognised, the NATO alliance was formed, the Marshall Plan rejuvenated Europe, atomic weapons ended the war with Japan, another war in Korea was fought to a stalemate, and the causes of civil rights and health insurance stumbled on. If those the times, then this had to be the man.

Other possible role models share Cromwell's distaste for democracy in action. Winston Churchill once summed up Stalin as possessed of "a cold and deep wisdom" as well as "a complete absence of illusion of any sort". Putin and Xi might happily accept such a chilling characterisation. In a democratic election, however, we need our leaders to be engaged in the getting of wisdom. We should also widen our talent search, by realising that, if these the times, then this must be the woman.