CYNTHIA NIXON is the latest celebrity to run for office in America; the “Sex and the City” star is trying to be governor of New York. If she succeeds, she will follow in a long line of celebrities-turned-politicians including Sonny Bono, Arnold Schwarzenegger, Jesse Ventura and most notably, Presidents Ronald Reagan and Donald Trump.

This may not be a uniquely American phenomenon. Beppe Grillo, a comedian, launched the Five Star movement, now Italy's biggest party. Silvio Berlusconi cultivated the celebrity style. George Weah, a footballer, has just been elected president of Liberia. Joseph Estrada, a movie star, was president of the Philippines.

Even conventional politicians are expected to show a bit of star quality. Al Gore failed in his run for president in part because his public demeanour was seen as wooden and dull (it was said he reminded women of their first husbands). The attempts in last year’s election campaign to create a personality cult out of Theresa May, Britain’s prime minister, failed dismally because she is a shy and reserved person. Emmanuel Macron achieved his success in France because he played up to a Napoleonic image.

Perhaps this is unsurprising. Leaders were traditionally chosen through heredity. To emphasise their authority, they dressed for the part; think of Henry VIII or Louis XIV. The leader had the best clothes, jewels and castles to demonstrate their status. Sometimes ordinary people were forbidden from wearing clothes or colours in a certain style, so that the elite could be kept apart. An alternative to monarchical rule was domination by the military; generals derived their authority from their uniforms as well as their guns.

Modern professional politicians have been around for only a century or so and become almost stereotypically bland in their grey suits and restrained manners. Watching “Darkest Hour”, it was hard not to think that Winston Churchill, with his drinking, smoking, tempers and mannered speech, would never survive the 24-hour news cycle. Many modern leaders are apparatchiks who have worked their way up through the party hierarchy, and have never done a job outside politics. They speak in a jargon that allows them to be understood by their peers, but sounds remote and incomprehensible to ordinary voters.

A celebrity, by contrast, has the benefit of instant name recognition and knows how to speak directly to the public. Like Reagan before him, Mr Trump uses simple language and expresses issues in black and white terms. Like a medieval monarch, he has his castles and his bling. Mr Schwarzenegger and Mr Ventura were elected on the back of their “manly” images; they were the kind of people who would get things done and end up on the winning side, as they did in movies and wrestling bouts. 

Such qualities are very useful in winning office, but not so helpful once power has been achieved. Real-life issues, with all their complexities and subtleties, cannot be dismissed with heartwarming or tubthumping slogans. So a lot depends on whether the celebrities realise this, and surround themselves with bright people. Henry VIII had his Thomas Cromwell; Louis XIV had Jean-Baptiste Colbert. Some of the worst mistakes of these monarchs came after the death of their key advisers. 

The celebrity leader could work if they merely play the role of a front man (or woman); a non-executive chair of the board. Reagan very much played that role in the 1980s. All the difficult decisions can be left to experts. Independent central banks already control many of the levers of economic policy. Other tough areas, like pensions or environment, can be hived off to commissions. Like a reality TV show, the public can then vote for the character they like most to present the show, and vote them off when they get bored. Rather than “King for a day”, celebrities will be King or Queen for four years.

The risk, of course, is that celebrities may not realise their own limitations, and think they are experts, regardless of their lack of knowledge. This is where Mr Trump is dangerous with his threats of trade (and actual) war and his philosophy of mercantilism (which has been dismissed by economists since 1776). But in an age of social media and celebrity worship, he is the kind of leader we are going to see more and more. We have seen the future and it twerks.