If a party of masochists set out to devise the hardest campaign to win in Britain today it would probably be inspired by bureaucrats, led by career politicians and endorsed by bankers. Its main demand would be unlimited immigration: so a lot like the case for staying in the EU as depicted by those who want to leave.

The counterpart story is the heroic interpretation of “Brexit” as the restoration of democracy to a nation traduced by Europhile leaders. That used to be the idiom of the fringe. Over the past decade, hardline scepticism was treated by pro-Europeans as cultural eccentricity; the ideological egg stain on the tie of unattractive politicians. Nigel Farage has shattered that complacency.

A remarkable feature of the election of two Ukip MPs in as many months is how unremarkable their demand for EU withdrawal has become. When candidates start talking about repatriating foreigners, as Mark Reckless did in Rochester, the parameters of debate have clearly moved well beyond abstract notions of sovereignty. Farage has cleverly recast a niche constitutional obsession as merely the means to an end – controlling immigration – that has mass market appeal.

A danger for those who would like Britain to stay in the EU is that, before the case can even be made, it is branded as an intellectual accessory of the metropolitan elite: just the sort of sick fetish you’d expect from Islington-dwelling guacamole-eaters who flinch at the sight of a St George’s Cross on a white van.

There is potency in a Ukip-style culture war on pro-Europeanism but probably not enough to swing a majority towards exit in a referendum campaign, when more material concerns – jobs and investment – are part of the equation. There is a growing feeling among Conservatives that Farage is a liability to the Eurosceptic cause. He does a great job of firing up an angry minority but an equally good job of alienating the rest.

A flicker of that anxiety was visible when Owen Paterson, the former environment secretary, set out his plan for an orderly EU withdrawal on Monday. Paterson’s big demand was the invocation of article 50 of the Lisbon treaty, effectively handing in Britain’s notice to leave the club. But an underlying motive behind the speech was to tug the Brexit argument away from lurid anti-immigration rhetoric and towards macroeconomics, trade and democracy. “Even people who are broadly in favour of withdrawal are unlikely to commit to the process unless they are assured that all the angles have been covered,” Paterson said.

That view reflects study of the Scottish independence referendum and the way Alex Salmond’s campaign was harmed by the impression that his white paper setting out the viability of a new state was cobbled together on the back of an envelope.

Paterson’s Tory allies fear that the “No to EU” cause will be lost if Ukip does the numbers and Farage is the frontman. The search is on for a less divisive figure. One option is to turn David Cameron from sceptical EU reformer to better-off-outer, which seems like a plausible goal since he has reliably yielded to every shove in that direction so far.

Pro-EU Tories say they are adding pressure of their own, urging Cameron to make no more concessions to the hardliners. Part of the problem is the prime minister’s reluctance to accept that chasing Ukip voters with Ukip’s own rhetoric has failed and that he would be better off changing the subject to his own record on economic management as quickly as possible – the course advised by the chancellor, George Osborne.

Cameron is still pinning hopes on a big speech he is planning to give on immigration. No 10 aides are poring over a policy Venn diagram looking for the place where things that appeal to people who vote Ukip overlap with things that can be agreed with Britain’s continental partners. Without identifying that sweet spot it will be hard for Cameron to go into a general election committed to campaigning in favour of EU membership. But it is because the hardline backbenchers suspect that no such sweet spot exists that they have forced Cameron to go searching for it.

Meanwhile, Labour struggles to get heard in the debate because it doesn’t accept that the in/out campaign has started. Ed Miliband had good reasons not to concede a referendum on EU membership: most businesses don’t want one and it would get in the way of other things a Labour government might want to do. But a perceived reluctance to “trust the people” feeds the charge of Westminster establishment arrogance that Ukip’s culture warriors want to pin on the pro-Europeans.

Clues as to how to tackle that argument are also found in recent Scottish experience. While Salmond’s weakness was a lack of economic rigour, the Better Together campaign was flawed by reliance on doom-laden arguments about financial viability. It was only in the final stages of the battle that the no side, helped by Gordon Brown, started pleading for the union as a version of Scotland’s future no less patriotic than SNP separatism.

The equivalent case will be harder to make for the EU, to which Britain’s attachment is comparatively recent and unromantic. But there is still a way to fight back against efforts to discredit pro-Europeanism as a kind of cosmopolitan liberal treason.

It involves combining the case made in terms of economic stability with questions about the character of the country we want to be: confident in our identity, tolerant, engaged with the world, not suspicious and embittered. A measure of how important that argument will be is that senior Ukip figures recognise it as a threat. “If the out case becomes an aggressive, nativist retreat to Little England, we’ll lose,” says one. That is why the shrewder Tory hardliners are talking up the reasonable-sounding economic route for Brexit.

The whole battle is horribly lopsided. The idea of a referendum has become an irreversible part of the public debate on Europe. But one camp is still tangled up in arguments about the timing of the fight while the other is already in full armour, marching on public opinion. It is mildly reassuring to supporters of Britain’s EU membership that their opponents fear defeat. It would be a lot more reassuring if pro-European politicians acted more as if they knew the campaign has already begun.