Angela Rayner, the former deputy prime minister, is the bookmakers’ favourite to be Keir Starmer’s successor. She is also someone who has recently given up vaping, according to the government minister Steve Reed, who had dinner with her at the weekend and told Sky News about it. These two facts about her – wanting to be PM and quitting vaping – are almost certainly connected.

Plainly, giving up vaping is preparation for the highest office. Rayner loves vaping: who can forget that fabulous photo of her, in the middle of the tax turmoil that led to her resignation last year, vaping in a dinghy off Brighton beach? You can get away with a huge amount of vaping as a middle-aged woman, owing to your fabled cloak of invisibility. I have vaped in committee room 10 in the House of Commons. I have vaped in the middle of an interview about whether or not vaping is bad for you. But I draw the line at vaping in the middle of the actual sea.

You can, of course, see why a prospective prime minister would think they need to quit vaping. You wouldn’t want a primary school teacher, priest or parkrun coordinator to do it, because of what it signals: a low-level but deeply held addiction, poor impulse control, a little bit of had-enough-of-experts contrarianism that doesn’t make sense from an authority figure. It’s a garden variety role-model thing.

If it set a bad example to voters, how would it play on the world stage? Would it weaken a prime minister’s hand in negotiations for her adversaries to know she’d bite your hand off for some Fuji Apple e-liquid? That she would give way on freedom of movement if someone would only lend her a charging cable?

It’s never enough for the holder of the highest office to be mostly decent, mostly self-disciplined – he or she has to be at the pinnacle of personal standards. It’s very stressful to watch, because you’ve collectively demanded standards that you know a human can’t meet – and then you have to bear witness to their deceptions, acted out for your benefit, as they fail and fail again to meet them. That’s why it was actually easier to witness Boris Johnson faced with a parliamentary inquiry than it was to see Keir Starmer nudge up to the same process. Johnson’s performance of probity was clownish and insincere by design, whereas Starmer’s has never had a trace of self-parody.

At the same time, it might arguably be a good thing for an ambitious politician to enter the fray wearing a minor human failing very visibly on her sleeve (or, more practically, a Lost Mary in every pocket). It would signal a new kind of promise: a prime minister who earned the power to represent us not by their exceptionalism, but by their ordinariness. It might also mark a useful realignment of public moralising and lived morality, which have peeled so far apart that a lot of the precepts of respectability are no longer true.

It was understood for decades that a prime minister could never have any kind of personal scandal, let alone be divorced, still less be divorced multiple times. Did Johnson capsize all that merely because his personal life paled into insignificance when set against his behaviour in office? Or did he illustrate that it was no longer true: that regular people didn’t care about prime ministers’ marriages, we all just plodded along assuming other people cared? Rayner-as-PM could conceivably do something similar: modernise respectability in her own way by openly parading a bad habit, but one which didn’t impede her performance and didn’t affect others (unless it aggressively smells of watermelon). But she has an uphill battle enough as it is if she wants this gig; the tax scandal that did for her deputyship will probably never be erased – and she’s also a woman in the comically male-led party of equality.

Some hypotheses for Reed’s revelation. Originally a fierce Starmer loyalist, he could simply be neutralising Rayner before she’s even decided whether or not to challenge for the leadership by reminding everyone that – whether she gives up or not – she will always fundamentally be unfit for the role because of all the past vaping (it’s a valid point of view – it is a ridiculous habit). Or he could have switched horses to some third option and be trying to get some momentum going in his own new camp with the reminder that a major competitor means business – and has already made the highest sacrifice (quitting vaping). Or he could now be Team Ange, and be signalling his support. It’s a frustrating array of contradictory possibilities, but that’s always the way with smoke signals.

• Zoe Williams is a Guardian columnist

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