Nigel Farage has erupted back into British politics like the sonorous belch that warns of a meal undigested; the bilious portent of a messy regurgitation. His campaign speeches come in familiar flavours with an edge of stale acidity – the scorn for a “Westminster class” that knows no patriotism; the lament for a country in social, economic and moral decline; the warning that mass immigration is gobbling scarce public resources and confected fury at betrayal by politicians who keep breaking their promises to end the scourge. It is the dish cooked up for Brexit, now back on the menu under the Reform UK brand. Farage claims to be satisfying a national appetite. He was all set to quit the domestic political fray, he says, but was called back to serve the people; his people. (The vanity is spicier, with a dash of messiah complex, this time around.) There has always been an electoral market for Farage’s product. Hardline nationalism tells a compelling story to people who feel insecure about their role in society, whose ambitions have been thwarted, who feel ignored by politicians and who correlate their unhappiness with an influx of foreigners. That cohort swells in times of economic distress but a party that speaks exclusively to those grievances doesn’t represent a majority in Britain, and never has done. The EU referendum was an exceptional case. It was won by brilliantly marketing a vague panacea to a disparate coalition that transcended traditional party lines – affluent middle-class southern Tories; disaffected “red wall” Labour voters in the north and Midlands. Even then, the official Vote Leave campaign knew that Farage was toxic and that the cause would be lost if he, and not Boris Johnson, were its figurehead. Prior to that, Ukip’s best performance in a general election was 2015, with 12.6% of the vote and a single seat – Clacton in Essex. That is where Farage is now standing. It is his eighth attempt to become a member of the Westminster parliament that he ostensibly holds in such low regard. The local odds are in his favour this time, but on a national level success for Reform is measured in trauma inflicted on the Tories. Farage boasts that he can poach support from both of the main English parties but that is a rhetorical device to project Reform as the insurgent challenger to a single beast, the political establishment, with two heads – Keir Starmer and Rishi Sunak. In reality, the damage is asymmetric. In marginal constituencies that swung behind Johnson in 2019, the bulk of switchers to Labour are people who voted remain in 2016 or, if they voted leave, now see Brexit as a mistake and don’t want to talk about it. Farage is not to their taste. The variable in those battleground seats is ex-Tory voters who are wary of Starmer and haven’t decided yet what to do on 4 July. They tend to be older, white, non-graduates, anxious about immigration and crime. They are doubtful that politics can make much of a difference, especially given that the referendum – sold as a transformative reboot of the system – left things feeling unchanged. Labour’s tally of winnable seats climbs higher the more of those voters either stay at home or switch to Reform. Repatriating them to the Tories has defined Sunak’s political method for months. Hence the compulsion to get someone, anyone, deported to Rwanda as a token of progress in “stopping the boats”. This explains also the curmudgeon-on-steroids election pledges – national service, mortice locks on pensions, stamping out Mickey Mouse university degrees – that sound cranky to anyone under the age of 70. That makes some kind of sense as a damage-limitation strategy. Sunak has effectively conceded defeat in the competition against Starmer to be prime minister. He is focused on saving enough Conservative MPs so that the party might be viable in opposition, cast into a shallow enough electoral hole that climbing back to power in a single term might be conceivable. For this to work, the prime minister needs to squeeze Reform out of the picture. That seemed feasible given the party’s lacklustre performance in local elections and its difficulty mustering a full roster of respectable candidates. Farage’s initial decision not to run looked like an early vindication of the Downing Street plan. With the subsequent volte-face he has snatched back that sliver of consolation. Sunak is left looking like a lame tribute act, suddenly upstaged by the appearance of the original star. This is an extraordinary trap for a prime minister to have manoeuvred himself into. There should be no equivalence between the two men. Farage is an astute campaigner and effective communicator, but he is not interested in responsible government. His declared aims are to shake up a campaign that he finds boring and to hollow out the Tories enough that he can occupy the husk of the party and enjoy making mischief when Labour gets bogged down in the hard business of government. He is a self-serving amplifier of impotent rage, not a purveyor of practical solutions. His talent is inducing panic in Tory MPs and beguiling rightwing media. He is a moth that persuades the flame to come to him. He has also professed admiration for Vladimir Putin, trailed sycophantically after Donald Trump and fraternised with some of the nastiest far-right parties across Europe. There should be a discernible boundary between Farage’s brand of malevolent provocateur politics and a Conservative party that still claims to represent a broad swath of the British cultural mainstream. Maybe Sunak can’t see the line or maybe he thought he was clever enough to dance around it without tripping. Either way it is a catastrophic misjudgment made all the more stupid and cowardly for being so predictable. How many more concessions must a Conservative leader feed to the ravenous right before discovering that it can’t be sated? What, if not to learn this lesson, was the point of Brexit? It certainly hasn’t served any other purpose. Theresa May offered the eurosceptics most of what they wanted and it wasn’t enough. Johnson gave them the rest. Not enough. There are still meddling judges from the European court of human rights to be vanquished; still an armada of migrants to be repelled. Still more blame and bitterness to be extracted from the seams of social and economic discontent cynically mined for Brexit. There was a moment when Sunak could have restored the old Conservative mode of politics. He could have honoured the pledge, delivered on the threshold of No 10, to govern with “integrity, professionalism and accountability at every level”. Or at least sustained the effort. Now it is far too late. The one campaign asset he had was the authority of a prime minister – the claim, by virtue of his office, to stand as a statesman. Then he surrendered even that. And for what? Gathering the crumbs of reheated Brexit that fall from Farage’s lips. Rafael Behr is a Guardian columnist