The Tory succession to David Cameron is becoming a triangle

The complex 28-sided EU negotiation is meeting a five-sided leadership contest

Liam Fox, the former defence secretary, has emerged as a leadership contender (Getty)

Liam Fox? Where did he come from? The surprise of last week was the emergence of the former defence secretary at the top of a poll of Conservative Party members as next prime minister.

It was a bit like polls in the early stages of the US Republican primaries, with lots of candidates and none of them emerging from the melee. Fox came top of the Conservative Home poll with 20.9 per cent, just ahead of Theresa May on 20.6 per cent. Then came Boris Johnson on 19 per cent, George Osborne on 15 per cent and Sajid Javid on 14 per cent.

Naturally, Fox’s top place was over-interpreted as a boost for the vote Leave cause. He had advertised his anti-EU credentials before the poll was taken, but as the only avowed Outer on the list you might have expected him to get more than just a fifth of the vote. This poll was taken before David Cameron’s draft EU deal was published, and perhaps when it is repeated Fox will do even better. Or, and this was the speculation of last week, perhaps Johnson will have joined him in the Better Off Out camp, which would shake things up again.

That speculation was stoked by Marina Wheeler, Johnson’s wife, who is a QC, setting out the reasons she thought the terms offered to Britain by Donald Tusk, the EU president, were not legally binding. Was she preparing the ground for her husband to lead the Leave campaign? Or was she setting out the Johnson family’s demands for this week’s summit?

No one who knows is saying and the rest of the bubble joined in the guessing game. Ed Balls, the former shadow chancellor, pitched in from Harvard, one of his academic posts. “Say what you like about George Osborne, at least he’s putting the country’s interests before his own on this issue, in contrast to some of his rivals,” he told Huffington Post. When Balls praises Osborne, you know something is up.

What is up is the complex interaction of a 28-sided international negotiation meeting a five-sided Tory leadership contest. This was triggered by the Prime Minister’s unintended announcement, in his Oxfordshire kitchen at the start of last year’s election campaign, that he would stand down before the next election.

I had assumed that Cameron’s lame-duck moment was deliberate, when he said: “Terms are like shredded wheat – two are wonderful but three might just be too many.” I thought he wanted to appear modest, not wanting to go on and on and on, as Margaret Thatcher had done, and wanted to emphasise the strength of the Tory team. But I now understand that he hadn’t intended to say it, and that Lynton Crosby, the campaign manager, and Craig Oliver, his director of communications, were furious about it because it was a distraction from their core messages.

All the same, I am told that he doesn’t regret it. It may well be that, if he hadn’t made his self-limiting announcement, the speculation about his future would have been more disruptive during the election campaign. But by now everyone would be expecting Cameron to fight a third election. Indeed, as we report, many Tory MPs want him to change his mind. However, I am told that he is not going to do so.

Now, though, we are seeing the consequences of his spontaneous decision to say what he thought. As Tony Blair found, the moment you fight the election you have said will be your last, the speculation about the succession becomes insistent.

That means, as Balls noticed, and he made the comparison with the Blair-Brown era, that the referendum campaign has become entangled in the calculations of the contenders for the Tory succession. It didn’t do the Labour government any good that Gordon Brown was positioning himself to take over, and it is not doing the debate about Europe much good that it has become so closely entwined in internal Tory politics.

Nor is it doing the Tory party much good that its leadership election will follow the referendum on Europe. Cameron has put off the choose-and-fight moment for longer than anyone thought possible, but now the split is coming. The weakness of the Labour opposition only makes this a more dangerous moment for the party.

I still think that Boris Johnson will declare, reluctantly, for staying in the EU. I think that a majority of Tory MPs will do so too, and that the British people will vote the same way. But I am not sure about any of those predictions.

The one thing I am sure about is that the referendum will not be the end of Cameron’s problems, even if he gets the vote he wants. I am told that he is determined to stay on at No 10 for the “vast majority of the parliament”. But the Tory split over Europe could be deep, and the pressure of the contest to succeed him will only grow and make governing ever harder.

Twitter: @JohnRentoul