Across Europe, rightwing nationalist populism is on the march. Britain is no exception. Polls are putting Nigel Farage’s Brexit party in the lead. If it does as well as expected in the European elections, it will be the second time Farage has pulled it off: in 2014, Ukip topped the poll with 27% of the vote. Farage’s relative success is partly the product of his intuitive understanding of how to deploy the populist playbook: whip up public disenchantment with the establishment, accuse the elites of thwarting the will of the people and offer misleadingly simple solutions to complex problems.

With voters so disillusioned with the two main parties, it’s a seductive formula. But his success is at least as much explained by the eagerness of mainstream politicians to yield to his brand of politics, rather than to challenge it. On Europe, Farage has only ever stoked anti-EU sentiment without ever offering constructive fixes. He has consistently got away with telling untruths: that the EU is on the cusp of creating a pan-European army; that EU membership costs the UK £55m a day; that three-quarters of British law is made in Brussels. He has repeatedly praised Norway as a model for the UK’s relationship with the EU in the past, but last week denied it.

Even worse is Farage’s recent history of deploying racist dogwhistles. During the 2014 European election campaign, he said he thought people had a “perfect right” to be concerned if Romanians moved in next door. He has said migrants with HIV/AIDS should be banned from entering the UK and has claimed 60% of people diagnosed with HIV every year were born abroad and that the NHS should be for “British people”. He also pledged in 2015 that Ukip would scrap much UK race discrimination law. During the referendum campaign, he unveiled the “Breaking Point” poster that depicted a queue of mostly non-white migrants, who actually turned out to be a group of refugees crossing the Croatia-Slovenia border. Last year, the Leave.EU campaign, co-founded by the Brexit party chairman, posted a tweet that featured an image of Sadiq Khan, inflated figures about the number of new mosques in London and dubbed the capital “Londonistan”.

Farage may now be trying to distance himself from all this. But it is part of the Brexit party’s identity: its leader, Catherine Blaiklock, was forced to resign in March after several shockingly Islamophobic social media posts came to light. And there are plenty of other Brexit party candidates with a range of unsavoury views in the mix: from Claire Fox’s refusal to disavow the Revolutionary Communist party’s support for IRA bombing campaigns that killed innocent children (she was a senior activist at the time), to Ann Widdecombe’s shameful invoking of the sacrifice of those who died fighting in the Second World War to set in context the costs of a no-deal Brexit.

Ann Widdecombe speaks during a Brexit party rally in Durham. Photograph: Danny Lawson/PA

Mainstream politicians have cravenly chosen to dance to his tune, in doing so facilitating a culture in which politicians can mislead and lie without consequence. Ed Miliband was lambasted by the left of his party for the mugs branded with the slogan “Controls on immigration” in the 2015 election. Yet Jeremy Corbyn has since made scrapping freedom of movement Labour policy.

But the left’s capitulation has been dwarfed by that of the right. Conservative immigration policy has become steadily more extreme since 2010. Despite wide public support for removing international students from a completely arbitrary immigration cap the government never had any hope of meeting, Theresa May has consistently refused to do so. The hostile environment, designed to make Britain a sufficiently cruel place that it drives out illegal immigrants, has ensnared people who have legally lived and paid taxes in Britain for decades, who have been denied NHS treatment and wrongfully deported. May has made it far harder for young people who have grown up in Britain to secure their permanent status: they face extortionate fees of thousand of pounds. The irony is May is an outrider: the public is far more pragmatic on immigration than the Conservative party; the proportion of the public whose hostility to immigration is driven by opposition to ethnicities and religions other than their own has fallen dramatically in the last few years.

On Europe, too, Farage has called the shots. David Cameron only promised a referendum on a vague question that required no firm proposition, and thus no honesty, from those advocating for Leave in order to quell support for Ukip. During the referendum campaign, senior Conservatives such as Boris Johnson borrowed liberally from the Farage playbook, misleading the public about how much leaving the EU would free up for the NHS and that Turkey was on the cusp of joining the EU. (Johnson has since falsely claimed he made no comments about Turkey during the campaign.) Both May and Corbyn have embraced the deceit of the Leave campaign, misleading voters that there is somehow a Brexit that involves no difficult trade-offs, rather than levelling with them that if it goes ahead, there will be painful consequences.

It’s not too late to challenge the untruths of the Farage brand of politics. But both parties are on the brink of the ultimate capitulation: delivering Brexit, in the naive hope it will make the Farage threat go away. But he stands poised with a betrayal narrative regardless of what happens next: whether politicians hold a confirmatory referendum; whether we get a soft Brexit that leaves Britain a rule taker; or whether there is a hard Brexit that acutely widens regional inequalities. By swallowing the Farage message that Brexit can help fix Britain, Corbyn and May are as much agents of his success as the man himself.