THERE’S something grimly compelling about watching a political quipster burst. We’re living with a Prime Minister whose stated aspiration, as a kid, was to become “World King”. The Conservative Party, the British state and its Tory media have taken decades to puff this empty narcissist into First Lord of the Treasury. But puff and puff they have.

Expanding and expanding like the Pillsbury Doughboy, this bouncing, born-to-rule dabbler has been confirmed again and again in his childish inclination that – for him and folk like him – all things will be made possible. Johnson’s growth has been facilitated by friendly editors and party fixers. They indulged his vices, spun his sloth and talked him up as the next indispensable man.

And having finally been invested with the authority and responsibility he seems to have coveted for so long? Now, Boris Johnson has deflated into a sorry-looking, soggy-bottomed boy. While the Tory party retains its undying grip on the English public consciousness, this sleepy Prime Minister’s personal ratings are at full droop. All the signs are the luck child’s blown his fortune.

It is important to realise Johnson’s indolent and directionless ministry is a symptom of what the United Kingdom now values in its leaders – not its cause. When he was asked why he wanted to become prime minister, David Cameron’s answer became emblematic of the entitlement and laziness of these new scions of Britain’s ruling classes.

“Because I think I’d be rather good at it,” Cameron said, with an air of a man who takes up a racket sport in middle age and is pleasantly surprised to discover he can still hit the ball. Perhaps more obnoxious, and certainly more revealing, was his quip to an old friend, shortly before the LibDems first planted him in Downing Street in 2010. “Just how hard can it be?” Cameron is reported to have said.

A more thoughtful politician – a more reflective human being – might have noticed the gradual hardening of Tony Blair’s rictus smile during his long years in office, the fact Gordon Brown wore his face like a map of the world, but young, smug and devil-may-care, for the likes of Cameron and Johnson, the weariness of the flesh is always because the other guy just doesn’t have your spunk. Always, that is, till you enter office, the world falls out of your gusset, and you start looking like your granny. As William Boyd said: “The last thing you know about yourself is your effect.”

Experience has been a harsh tutor. As the last three occupants of Downing Street must now realise, the answer to Cameron’s rhetorical question is: “Pretty damn hard.” The Scottish context is not so different. While ickle Douglas Ross runs the line and chases TV cameras across Scotland, Nicola Sturgeon’s shift over the last six months has been a thankless slog no faint-heart has any business attempting.

It seems remarkable that anyone could become the leader of a major political party with no strong idea what they want to achieve in office – but if you incentivise the election of plausible charlatans, if you value slogans over policies, the ability of politicians to quip loveably about the bin fire of their private life and their terminal capacity for dishonesty, what do you expect will happen?

We get the kind of bozos the media decide we deserve. And just as there are pleasures in watering and cultivating political careers – the hacks will also enjoy sawing through the beanstalk and watching the political giants they create crash painfully to Earth.

Politically, Johnson has no idea what his golden egg looks like. During his public life, Johnson has posed as the one-nation Tory and a dynamic wrecker, a proponent of compassionate conservatism and a head of government happy to appoint a raft of career psychopaths to high office. He is at once pro-European and anti-European, the liberal Tory and scourge of the nanny-staters, leading an administration which now wants to mandate you to shrink your waistline. Johnson has always been an ideological blob. The fact his government has been in intellectual free fall since he took office should surprise no-one.

Boris Johnson is all too emblematic of a whole generation of Sir Politick-Would-Bes, who seem to think politics is some kind of vision quest, as if high office is mainly an opportunity for self-discovery and personal growth – rather than an opportunity to get your hands on some of the social and economic levers which can be used to change the society you live in and the economy you live with for the better, however you understand the idea. Justice is felt, most often, in small places close to home. So is injustice. You’ll rarely find it in soaring speeches or witty answers, in nifty wordplays or funny metaphors. All of that is evanescent. None of that lasts.

I’ve had the chance to meet a bunch of politicians in my puff, bearing almost every kind of political stripe, from north Oxford Tories to apologetic LibDems, “as a socialist” firebrands and diehard nats. In my experience, most politicians are coming down with general values and principles. If prompted, they all can be relied on to reach for generic nostrums about social justice and fairness. They will all declare themselves committed to vague ideas of equality and progress. All of which is fine, as far as it goes.

But as the Johnson leadership has cruelly exposed, one thing too few of our politicians have, remarkably, is any kind of concrete agenda. The older I get, I find myself growing more and more intolerant to this approach to politics. Instead of asking candidates “why do you want to be a politician?”, we should be asking them “what do you want to achieve if elected? Give me three priorities”.

There are admirable exceptions – in which I’d include my own MP, about whom I’ve written fondly in these pages before. In Glasgow Central, Alison Thewliss has tackled period poverty, the rape clause and, most recently, harried the Home Office tirelessly on its dead-eyed, dumb-as-a-brick unwillingness to see the scourge of intravenous drug use in her home city through the lens of public health rather than the criminal law. Local activist Peter Krykant has exposed himself to the full jeopardy of the criminal law in his converted Ford Focus, beginning work this month on a mobile safe consumption space in the city.

Last week, Priti Patel’s department confirmed “we have no plans to introduce drug consumption rooms and anyone running them would be committing a range of offences including possession of a controlled drug and being concerned in the supply of a controlled drug”. It’s all true under the law – but spectacularly misses the public health point. I’m confident Alison would have a good answer to my question. In policy terms, she’d be able to come down to brass tacks. Her outlook is emblematic of the idea that good politics must be constructive, rooted in the real world, and rooted in the needs and jeopardies your constituents find themselves in. As Boris Johnson still can’t understand, everything else is just PR.

As a democratic party with an open selection process, the SNP now has the chance to ask itself these questions. There’s no droit de seigneur, no rotten boroughs, no lifetime appointments insulated from the membership choosing its representatives. In Holyrood’s ministerial ranks, Shirley-Anne Somerville in Dunfermline, Fergus Ewing in Inverness and Nairn and Ash Denham in Edinburgh East are facing local races to justify their places in Holyrood. Elsewhere in the SNP caucus, Colin Beattie in Midlothian North and Musselburgh, David Torrance in Kirkcaldy and Christine Grahame in the Borders are facing selection battles. In Glasgow and west-central Scotland, there are contested selections in Cunninghame North, in Glasgow East and Cathcart and Greenock and Inverclyde.

If you find yourself voting in a selection contest – if you find yourself choosing between alternative contenders to contest a Holyrood seat – I’d encourage you to consider not just the pitch of their ambition or the campaigning zip they promise, but ask yourself whether these are folk with concrete ideas to lift up the community you live in. Are they people you could confidently install in ministerial office, who’d arrive at their desks with more than an empty paper and half-empty empty heads?