Theresa May Mark One buried UKIP. Theresa May Mark Two is digging it up. That is the only conclusion one can reasonably draw from today’s Opinium poll for the Observer, which shows Labour on 40 per cent, as last month, the Conservatives on 36 per cent, down six points, and UKIP on eight per cent, up five points. The movement from the second to the third could scarcely be clearer.

That rise in support for what many will still think of, wrongly, as Nigel Farage’s party isn’t because of rebooted support for him. Nor will voters be enamoured with the charms of Gerald Batten, of whom most of them will never have heard. The driver of this result is plainly the Government’s new Brexit policy.

25 per cent of those polled approve of the way that the Prime Minister is handling Brexit, down from 30 per cent last month, while 56 per cent disapprove, up from 45 per cent last month. Her net approval rating was minus eight per cent last month; it is 24 per cent this month. The percentage of those who believe that Brexit is one of the most important issues facing the country is at its highest ever recorded by Opinium – 51 per cent this month (it was 42 per cent last month). Overall, 32 per cent of those surveyed supported May’s Brexit plan and 31 per cent opposed it.

The EU referendum result killed UKIP. After all, what was the point of supporting a party which aimed to make Britain independent once the British people had voted for precisely that? The cause of Brexit was handed overnight to the governing party, which now had an instruction from the electorate to deliver it. During the period between the referendum and last summer’s general election, Theresa May presented herself as the woman who would fulfil that mandate for “citizens of somewhere”: “Brexit means Brexit”.

In her speech to the Conservative conference of 2016, she announced the moving of Article 50, and drew red lines for the negotiation. “We are going to be a fully-independent, sovereign country, a country that is no longer part of a political union with supranational institutions that can override national parliaments and courts. And that means we are going, once more, to have the freedom to make our own decisions on a whole host of different matters, from how we label our food to the way in which we choose to control immigration.”

This was the thread that ran through other big speeches – Lancaster House, where she said that “no deal is better than a bad deal”; Florence, where she outlined a three-basket approach to regulation, alignment and divergence; and Mansion House, where she confirmed the practice that would underpin it: “a comprehensive system of mutual recognition”. And as she put it in that first speech to her party, “we are not leaving only to return to the jurisdiction of the European Court of Justice”.

You may support or oppose this approach – drawn together in DexEU’s Brexit White Paper, published last week on ConservativeHome. But, whether you like it or not, it kept the Conservative vote bobbing around at 40 per cent or so, with those former purple voters safely tucked away inside the blue column. At last June’s election, the Prime Minister pushed the Tory share up to 42 per cent, a total that David Cameron, Michael Howard, Iain Duncan Smith and William Hague would have killed for.

Yes, she none the less lost her majority. To which there can only be one reply – namely, that if you can’t win a majority on 42 per cent, you don’t stand a prayer of winning one on 36 per cent, at least if Labour’s share is higher than yours. True, the Opinium poll is only one survey, but it is in line with last weekend’s Tory ratings drop in a Survation poll; a fall in a YouGov survey which followed it, and a further poll from the company later that week which showed “opinion turning against the Chequers Brexit deal”.

The Prime Minister will claim that the new plan is in breach neither of her red lines, nor of the Union Flag-wrapped speech which Nick Timothy wrote in 2016. But it is clearly a radical departure from mutual recognition. Most voters wouldn’t be able to explain the technical difference between it and ongoing harmonisation. But they have an acute sense of political smell. If May, therefore, says that nothing has changed, but David Davis and others say that a lot has changed, who are they more likely to believe?

These are sort of voters who ask the local MP: “why haven’t we left yet?” They are not political sophisticates. But they are part of the backbone of the country. On Friday, we urged May to go on the Andrew Marr Show today, and make her case: explain where she is now, how she has got there, why she changed her approach and what she plans to do next. Today’s Mail on Sunday confirms that, even yesterday, Davis was poised to be the show’s star guest. But at the last moment, the Prime Minister has bowed to our advice.

She is likely to argue this morning, if a piece by her in the Mail on Sunday is a reliable guide, that it is her plan or nothing – that, if her party doesn’t back it, the Commons will move collectively to postpone moving Article 50. If she does, she will have a strong point: that’s a serious possibility, and Conservative MPs must factor it in to their calculations. They must also ask how changing Party leader would make any material difference in a Commons that was pro-Remain pre-election, and is still so in sympathy now.

But May’s new plan isn’t the end of the Brexit negotiations. Rather, it’s the end of the beginning – the point, atrociously late in the day, when she has finally revealed her hand. It is an opening bid, not a final position. What will happen when the EU, as it is bound to, pushes back – on services; on free movement; on the ECJ? If the Government makes further concessions, wavering Tory MPs will ask themselves whether a Brexit on such terms is worth having – and whether the Prime Minister is worth keeping.