Was this the moment Kemi Badenoch was handed the Conservative leadership?

You would have thought by now it would have occurred to even the most old-fashioned MPs that judging a candidate’s suitability for office by whether they have children or not looks foolish.

Indeed, it does seem to have occurred to Christopher Chope, the 77-year-old veteran Tory MP for Christchurch, in mid-sentence, when he explained why he was supporting Robert Jenrick for the Conservative leadership. “Much as I like Kemi, I think she is preoccupied with her own children,” he said on ITV.

A warning light must have flashed in his brain, because he went on: “Quite understandably…”

The warning light was still flashing as he remembered that Jenrick has young children, too, and that he was suggesting that a mother is automatically weighed down by childcare responsibilities more than a father: “But I think Robert’s children are a bit older.”

In fact, Badenoch’s youngest, of three, is five and Jenrick’s youngest, also of three, is eight. No wonder Chope walked into a wall of instant condemnation.

Worse than that, from his point of view, is that he gave Badenoch the chance, in the GB News debate on Thursday, to dismiss his comments in a fine put-down that allowed her to emphasise how hard she worked, and to come across as both competent and human.

Jenrick himself was forced to praise Badenoch as a “good mother”, and said he hoped he was a “good father”, too – but the damage done by the Chope endorsement was done.

Subliminally, the Tory members in the audience were reminded again of the parallels between Margaret Thatcher and Badenoch – strong characters with stage presence who overcame sexism and used it to their advantage. Thatcher was asked at selection meetings in the Fifties how she could manage being an MP and bringing up children; it is extraordinary how little progress some in her party have made since then.

Chope seems to have been confused by feminism. When people make the point that women tend to be responsible for a disproportionate share of childcare, this is not intended as an argument for excluding women from demanding jobs. Which was the implication of what Chope said next – with alarm bells and sirens going off by now as well as the flashing lights: “I think it is important that whoever leads the opposition has an immense amount of time and energy.”

Yes, being the leader of a party is an exceptional job, which is why it is quite wrong to make assumptions embedded in old social norms about how any individual will perform.

Chope has made the opposite of the Leadsom-Vance mistake, which is equally sexist, which is to assume that a woman without children is somehow less qualified for a leadership role than a man without children. Andrea Leadsom destroyed her leadership bid in 2016 by saying that “I have children” and therefore a stake in the country’s future that Theresa May did not. JD Vance, Donald Trump’s running mate in the presidential election, put a spoke in the Republicans’ campaign wheel when he complained that the women running America, including Vice-President Kamala Harris, were “a bunch of childless cat ladies”. He has been trying to explain himself ever since.

It is an unforgivable mistake to make, to attack a female politician’s personal life in a way that would not be done to a man. In modern times – that is, since about 1965 – these kinds of personal attacks always backfire.

In Chope’s case, it looks as if cosmic justice has been done. All he has succeeded in doing is ensuring that his preferred candidate loses. Badenoch was able to use his foolish comment to shine in the TV debate on Thursday. She would have done better than Jenrick anyway, coming across as more engaged, more thoughtful and more energetic.

But his silly sexism allowed her to add to her pitch that she is someone who can be a devoted parent and good at the top job. If the betting markets have got it right, it looks as if she will get the chance to prove it.