Theresa May, U.K. prime minister, departs number 10 Downing Street to attend a weekly questions and answers session in Parliament in London, U.K. (Photographer: Luke MacGregor/Bloomberg)

How Could May Get a Brexit Deal Past Parliament? You Do the Math

(Bloomberg) -- Theresa May’s government and Jeremy Corbyn’s opposition Labour Party have been in talks for a month in search of a Brexit compromise. But hanging over the negotiations is a simple question: Even if May and Corbyn reach a deal, could they get it through Parliament?

Running the numbers throws up a solution that’s potentially the most perilous of all for May: offer a second referendum to ratify the deal. Here’s the math:

Target: 318

There are 650 members of parliament, but 11 of them don’t vote, which means May needs 320 for a majority. Two MPs on each side of every vote do the counting, so aren’t included in the tallies. May needs to get to 318 to be sure of winning a vote.

But actually she needs more than that. May doesn’t simply need to win one vote. To get Brexit through Parliament she needs to pass her Withdrawal Agreement Bill, which means winning vote after vote after vote. That’s why her office keeps talking about a “stable majority” -- one that will survive the occasional MP going missing, or rebelling on some aspect of the bill.

Conservatives: 196

This is the number of Conservative MPs who voted for May’s deal the first time she tried to get it through Parliament, on Jan. 15. It’s true that she managed to get this number up to 277 by March 29, but by softening the divorce terms further to get Corbyn’s support, she’d probably lose many of the Tories she picked up.

How Could May Get a Brexit Deal Past Parliament? You Do the Math

Labour: 125

Labour has 246 MPs, but how many of them can Corbyn deliver? Informal votes on Brexit have indicated that there could be as many as 121 Labour members of parliament who are willing to rebel against the party whip in order to stop Brexit. That leaves just 125 potentially backing a deal.

Total: 321

This doesn’t pass the “stable majority” test. But what if May went further, and offered a referendum on her deal, something that Labour’s Brexit spokesman Keir Starmer keeps telling the Conservatives will be needed to get most Labour MPs on board? (May has repeatedly said she opposes another plebiscite.)

Conservatives With a Referendum: 150?

We’re now in the realm of deep speculation, but adding a referendum would cut the number of Tories backing the deal. The floor for May’s support is probably around 150: That’s the so-called “payroll vote,” people who would lose paid or unpaid posts if they rebelled against the government. Agreeing to a referendum would provoke resignations from this group, but for our purposes, they’re offset by the number of rank-and-file Tories who never ever rebel against the whip. And a few Tories who have been voting against May could potentially come on board if another plebiscite were on offer.

Labour With a Referendum: 200

We can be clearer here, because in the indicative votes process, Labour MPs were told to support a referendum. Second time around, 24 voted against, and a further 16 abstained. That leaves more than 200 willing to vote for another referendum.

Total with a Referendum: 350?

That’s a stable majority, and it might even go up if smaller opposition parties such as Scottish Nationalists, the Liberal Democrats and Change U.K., who all support another referendum, joined in.

The trouble is it might involve only a minority of Conservative MPs and in those circumstances, the prime minister would struggle to survive. Still, May has said herself she’ll quit once the deal is done.

How Could May Get a Brexit Deal Past Parliament? You Do the Math

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