When Cherie Blair got pregnant in Downing Street, to create the first baby born to an incumbent prime minister since the 1840s, the general response was a muted surprise and respectful congratulations. Nobody was anti-baby. At the same time, a prime minister was a public servant, not the head of a dynasty or a character in a soap opera; we weren’t about to make baby Leo into a commemorative plate. We were, in the main, steadfastly neutral towards this baby, neither for nor against him.

Contrast the forthcoming bundle of joy from Boris Johnson and Carrie Symonds: supportive newspapers are billing this event somewhere between a royal baby and a second coming. The front cover of the Sunday Telegraph looks like Hello! magazine, the great, beaming face of Symonds carefully angled so that Johnson, kissing her in profile, doesn’t look anything like as raddled as usual. “No 10 wedding – and a baby too!” the headline croons, as though these two heartwarming facts were entirely unrelated. A radio host tweets, “some much needed happy news for the country”, and a nation is left scratching its head and rubbing its eyes: how is this supposed to be for the country? Isn’t the prime minster constantly having children?

Facebook Twitter Pinterest ‘Johnson, kissing her in profile, doesn’t look anything like as raddled as usual.’ Photograph: Apples_Symonds/Instagram

But all the personal critique is quite half-hearted. I don’t care that Johnson will be on his third marriage, or that his fiancee is 24 years younger than him. I wouldn’t care if he didn’t get married. This tub-thumping moraliser, the prime minister who has happily spun a few bob out of castigating single mothers, dares us with his happy-family pantomime to use those moral arguments against him, and who knows, perhaps they would be effective. But I don’t believe in policing people’s personal lives. Conservatives are incredibly good at borrowing principles they don’t hold to score a point. (Topical example: having had no interest in equality for the previous six decades, suddenly they’re the most fearless crusaders against sexism and racism when they’re defending Priti Patel.) The left, typically, is bad at it, and should be proud of that.

Nor am I wild about the argument that the baby is a distraction, that news of its forthcoming arrival is being wheeled out to distract us at a difficult time for the government, when crises are all around, only roughly half of them of its own making. Perhaps Johnson is so cynical, maybe he’s looking to maximise the feel-good or dead-cat potential of his progeny; maybe they’ll be popping out a conveniently timed sprog every other year until all disasters have passed, by which time nobody will be able to count the prime minister’s children.

Yet when you try to second-guess a politician who uses his personal life to calculated effect, you’re drawn into a cynical feedback loop. You start off questioning his motives in buying a dog: pretty soon, you’re suspicious of the dog (it’s looking cute on purpose, because it knows another permanent secretary is on the way out). This is win-win for Johnson – either we take his news at face value, and rejoice in it, or we scrutinise it for manipulative intent, becoming cynical ourselves in the process, normalising a culture of mistrust. I would prefer to be knitting a tiny hat.

Yet there is a reason to balk at the new politics. The prime minister, present in Technicolor for this personal news, has been absent as a politician: invisible in the flood-hit areas; extremely late to, and so far nonsensical on, the matter of coronavirus. He was so conspicuously absent for nine days of last month, holed up in the foreign secretary’s country retreat, that wild rumours started to circulate as to what he was doing (the weirdest being that he was writing another novel). Perhaps his supporters will use his baby announcement as the reason for that – ah, it all starts to make sense, he was decorating the nursery – but this too is extremely unusual, not just in politics but in any job, to take nine days of paternity leave before the child is even born.

Westminster's worst-kept secret: but will it lead to a baby bounce? Read more

His pattern of behaviour, and the way in which it instructs us to treat him, is not as a politician or, indeed, a professional at all but as a TV celebrity. It would be absolutely typical for a Kardashian to say nothing of substance and save all transparency for personal announcements on Instagram and to favourable media; it would be typical for a Trump, or any other politician in the showbiz model. There is an implicit servility – there is nothing reciprocal in that relationship, ours is not to question but to behold. Unlike a royal baby there’s no pomp, just an atmosphere of constructed jollity (they’re celebrities, after all, not royals). It is unnerving, beyond anything else – and it is this televisual razzle-dazzle, rather than any baby, that is unprecedented in an incumbent prime minister.

• Zoe Williams is a Guardian columnist