The obvious thing to say about Theresa May’s decision to allow herself to be seduced by the glamour of a Vogue fashion shoot is that it looks irreducibly terrible. Tone-deaf, self-indulgent, frivolous – whatever the angle, not one of them is flattering.

This is the narrative: not even Annie Leibovitz, mistress of digital manipulation, can restore dignity to a prime minister who chooses to take part in a fashion shoot while presiding over a car-crash nation. A leader anxious to look as if she is in touch with her just-about-managing fellow citizens wrestling with austerity and Brexitwill be pictured flaunting clothes that will certainly not be available in your average Marks & Spencer.

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It’s no defence that the idea was conceived in the pre-Trump era – maybe even in the heady days when it must have seemed a reasonable bet that by the time the pictures appeared in April, Hillary Clinton would have joined May herself and Angela Merkel in a trilogy of female power unprecedented in the history of the western world.

If that had been the appeal (and who can but mourn its loss) then the smart thing to do on 9 November, immediately after the call to Trump Tower, would have been an urgent email to the editor’s office in New York.

Now it seems likely that on her first visit to Washington as prime minister, she will have prepared the ground for her encounter with a man notorious for reducing women to objects by presenting herself on the pages of American Vogue as, well, an object.

And that is not the end of it. Even more damaging is that her decision to submit before the eyes of the world to the narcissism of fashion could easily become one of those defining moments: like Margaret Thatcher in the tank turret looking like a cross between Boudicca and Lawrence of Arabia, this one misjudgment might easily become a signifier of all that is flawed in her prime ministerial style. Here is a woman already perceived to lack strategic nous, a prime minister with no mandate from the electorate, a politician who, even if she says the right thing, carries on doing the wrong one.

Where was the sage advice that it would not be a good look for soft-focus images of the prime minister to be in the news at the start of a financial year that will remove many hundreds of pounds in tax credits and housing benefit from the incomes of many thousands of families? What part of a wise prime ministerial strategy might include juxtaposing austerity with an appearance in the pages of the global handbook of conspicuous consumption?

If you own a home, you should read this. Thousands of homeowners did this yesterday, and banks are furious! Do this now before it's...And yet, while all that is true, she is on to something important. First, British fashion is big business and the US is a big market. That is at least part of the reason why American Vogue’s British editor, Anna Wintour, was made a dame in the New Year honours.

Second, fashion is on to a trend: the world has just got serious about politics. Last month Teen Vogue had a smash hit with a blistering leader about Donald Trump “gaslighting” the country (to gaslight, it helpfully explains, is to psychologically manipulate a person to the point where they question their own sanity), which far outstripped the second most-read feature of the year, on the right way to apply glitter nail polish.

A generation ago, UK media strategists realised Woman’s Hour and the Jimmy Young Show were a more effective way of reaching ordinary voters than the broadsheets and political TV. But this is something different. After Brexit and Trump, voters who for years rarely had cause to trouble a polling station have become passionate. The business of fashion magazines is spotting trends – and this year, at least, politics is fashion.

That is not the same as saying that fashion is politics. Yet it is slowly becoming so, as the business of how women in power express their political personalities goes mainstream. Leibovitz, the portraitist who did the American Vogue shoot with May at Chequers, is always interested in women and power and the power of women. She has rescued the Queen from nation’s grandmother status and returned her regal presence. She takes Hillary Clinton and Michelle Obama, both regulars in American Vogue (Obama has been on three covers) and makes them softer, and more traditionally feminine, than people would expect from their public presence as representatives and associates of power.

Clinton was open about the conflicting pressures of power and appearance, and compromised by adopting the invisible androgyny of the Angela Merkel trouser suit. But May has never conceded her interest in fashion to the demands of political convention. She set out to normalise the idea of serious women being serious about fashion too. She was in the pages of British Vogue before she had even been elected an MP.

She has developed style as a form of political communication. Where her male colleagues might brief select correspondents to trail a policy development, May declares her intent with a fashion statement that is often flashier than what she eventually says. Where she is cautious politically, she is bold (at least, fashionistas might mutter, by Maidenhead standards). Like the vicar, the vicar’s daughter dresses for the job. In a world where political debate is conducted by tweet, a fashion shoot in Vogue might be read as a manifesto. If the prime minister has a future, it will need to be a good one.

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