There are not many professions where lack of expertise can be called a quality. If you need your accounts done, you go to a career accountant. Anyone who needs an appendix removed would steer away from the “insurgent” surgeon who takes pride in never playing by the rules of the “medical bubble”. Politics is unusual in sustaining a myth of the heroic amateur.

Wariness of slick operators and ambitious apparatchiks is a healthy instinct. There are people who don’t share Jeremy Corbyn’s beliefs yet still applauded his rise as a rebuke to New Labour’s lapse into calculated vapidity. But a slap landed on the face of conventional politics is not proof that conventional wisdom is all bunk. David Cameron is prime minister because he played the game by the rules and won. His elite pedigree and elastic principles were obstacles to affection, but not to victory.

The Corbynite left might rebut that view by citing Ed Miliband’s handicap as an Oxbridge-educated spadocrat – a defective imitation of the thing he sought to supplant, practically inviting voters to stick with the genuine article. But Miliband was not the only threat that Cameron saw off in May. He also trounced Nigel Farage: the self-described antidote to cosy consensus, burster-in-chief of Westminster bubbles.

Labour’s post-election implosion has overshadowed Farage’s humiliation in May, so let’s recap. In 2014, Ukip topped the poll in European parliamentary elections. Tory conference that autumn was disrupted by two defections and rumours of more. Re-badged “Kipper” candidates won both of the subsequent byelections.

Then it went wrong. Farage scoured the land for a friendly constituency; an open door to parliament. He chose Thanet South, but southern Thanetters closed the door in his face as did voters in every other seat bar one. Farage tendered his resignation to the supreme party authority – himself – and rejected it. A row blew up between the loyalists to the original cult of saloon bar bravado, and the advocates of professionalisation who understood that bibulous swagger and nudge-nudge tolerance of bigotry had scooped up as many voters as they ever would, while alienating many more.

The modernisers feared that Farage was a liability in pursuit of the party’s founding dream – rupture from the EU. The loyalists won but the schism persists, reflected in confusion over Farage’s role in the anti-EU referendum campaign. He initially endorsed the claim of one group (Leave.EU, which is funded by Ukip donor Aaron Banks) to be the lead voice urging exit. Now he proclaims equal support for the rival Vote Leave group, under whose banner Eurosceptic Tories are mustering, along with business leaders, a few Labour MPs and Douglas Carswell – Ukip’s lone representative in the Commons. Farage looks like a gatecrasher at the ball he once dreamt would be held in his honour.

Ukip’s marginalisation is partly a function of the electoral system. It is unfair that 4.5m votes should yield a solitary seat, even if liberals are glad of it. But Farage was not unaware of the way MPs are chosen. Ukip targeted seats on the basis of their vulnerability under first-past-the-post, and was still beaten. It happened because voters respond differently to a mid-term election (where incumbent governments invite punishment for being the government), and general elections(where the dominant question is whether someone else should be trusted with power.)

Farage failed because enough people recognised that the limit of his capabilities was channelling anger, not crafting solutions. He could run a piss-up in the brewery of opposition, but that is a different skill to making potable beer. Farage didn’t merely fail to land a killer blow on Cameron, he did the prime minister a favour (and not just by taking votes from Labour). He marked out a boundary of civilised conservative politics and stood on the wrong side. He indulged cranks, obsessives and racists, many of whom would otherwise have been contaminating the Tory ticket.

In the lexicon of anti-establishment populism there is no greater insult than to label someone a “career politician”, since that implies the unprincipled pursuit of power for its own sake. But politics is a full-time job for which seeking power is part of the deal. Rewarding a semblance of professionalism is a reasonable, indeed often a principled basis on which to vote. Farage is a career politician whose career has been stunted by amateurism. Corbyn is a career MP whose chosen specialism is resistance to whatever the government of the day, Labour or Conservative, is doing. His motives may be pure. Voters can scale the heights of respect for that high-mindedness, without ever seeing it as a qualification to govern.

By contrast, Cameron and Osborne struggled throughout the last parliament to convince people that their hearts were in the right place, but their most vulnerable moment came in 2012 when the “omnishambles” budget unravelled and the economy was doing the opposite of what had been promised. Miliband let them off the hook by insisting that the Tories’ greatest offence was an excess of ideology (or “principle” as it is called when the left describes itself) as opposed to rank incompetence.

The centre of British politics is often imagined to be a location on an ideological spectrum between state-heavy socialism and unregulated market capitalism. But it is better understood as a zone of cultural respectability, occupied by the party that persuades enough people of unfixed allegiance that it knows what it is doing, thus making it safe to care less about politics. A weak opposition demands that people care more, and tries to rouse them by shouting. When that doesn’t work, public acquiescence to the status quo is treated with contempt – the electorate as dumb turkeys, brainwashed by the media into voting for Christmas.

There is a more generous view of the way democracy works. It is that people may not like their leaders, having been angered by mean-spiritedness and mismanagement of public assets (and the Tories supply ample amounts of both); but when polling day comes an intuitive judgment is made of whether the other side is adequately acquainted with the difference between its arse and its elbow. Amateurs can score endless points in opposition. When it comes to choosing a government, voters have a persistent habit of turning to the professionals.