Why I now think the choice is finely balanced between May’s deal and a new referendum

The House of Commons debate on the Brexit deal begins on Tuesday and is expected to conclude with an important vote a week later

The big question is now this: if the Labour shadow cabinet decided in favour of another referendum, would there be a majority in the Commons for it?

There may be 20-30 Conservative MPs who would prefer a referendum to May’s deal; and there may be 20-30 Labour MPs who oppose a referendum and would prefer the deal.

The DUP is opposed to a new referendum, so the government starts with a majority of 13, plus one Liberal Democrat, Stephen Lloyd, and possibly Sylvia Hermon, the independent unionist. The SNP, the rest of the Lib Dems, Plaid Cymru and the Green (Caroline Lucas) all support a second referendum.

For a vote in favour of a referendum to win, then, there needs to be nine more Tory rebels than Labour ones. If there were, for example, 30 Tory supporters of a referendum (Jo Johnson, Sam Gyimah) and 20 Labour opponents (Caroline Flint, Ian Austin), a referendum could win. Those numbers are hard to predict.

A referendum is not a simple option, though. There isn’t time to hold one under normal rules before 29 March, so a referendum amendment would have to include a clause instructing the government to postpone the Article 50 deadline. It may be that the UK government has the power to revoke its Article 50 notification – the European Court of Justice will rule on this shortly. Or it may be that the UK government would have to ask the EU27 to agree to an extension.

A referendum amendment would also have to specify what the question would be. I think this has been more or less settled, although the hard Brexiteers have not yet realised it. It would be May’s deal vs Remain. At most 100 MPs advocate a no-deal Brexit, fewer than one sixth of the total. In any vote on the options to be put on the ballot paper, “leave without a deal” would lose.

The other “question about the question” is whether Labour would support May’s deal being on the ballot paper. In a referendum, Labour would have to campaign for Remain and against May’s deal – the referendum could not be on an alternative deal that hasn’t been negotiated yet. So May’s deal has to be the other option on the ballot paper, or a referendum amendment would not win in the Commons.

Then there is the question of when the Commons might vote on a referendum. One of the amendments to the meaningful vote motion on 11 December could make ratification of the withdrawal agreement conditional on a referendum. Or, after the deal is defeated and then a Labour motion of no confidence in the government is also defeated, it could be one of the options to which the House of Commons turns.

Finally, there is the question of how a vote in the Commons could force the government to hold a referendum. This is where the flexible British constitution starts to break. The opposition can propose amendments to bills, and to some motions, requiring a referendum, but a referendum itself would need legislation, which is controlled by the government.

Ultimately, if the government failed to carry out the wishes of parliament, the House of Commons could change the government. But suppose it didn’t want to, because the alternatives would be a general election or a minority government led by Jeremy Corbyn? Then the question is whether, on something as important as this, a government could really ignore a majority in Commons.

I don’t think so, and I get the impression Theresa May doesn’t think so either. I think she is preparing to fight a referendum on her deal in case she is forced to do so by parliament. That is partly why she is willing to take part in a TV debate with Corbyn, why she is touring the country and why she is encouraging friendly newspapers to run campaigns to support her deal. “She’s running the 2017 general election very well now,” a cabinet minister commented to The Sunday Times.

This attempt to influence public opinion is mostly about putting pressure on MPs to vote the right way, but it has a second purpose as a dry run for a referendum campaign.

It was notable that Michael Gove, the environment secretary, told Andrew Marr this morning: “There may be a majority in the House of Commons for a second referendum.” He was trying to scare Tory Leavers into backing the government’s deal, but he sounded as if he was already expecting another referendum. Indeed, he slipped up and referred to what he’d said in “the last referendum campaign” before correcting himself: “God forbid there should be another one.”

I think May hopes to win the vote (or votes) on a referendum – and that defeating that option will allow her, eventually, to get her deal through parliament. But if parliament votes for a referendum, I think she expects to hold it, fight it and win it.