David Cameron is delivering a statement in the Commons about the EU renegotiation, following his late night deal in Brussels last week. Opposite him, he will see near-unqualified support. Though plenty of Labour MPs have misgivings about various dimensions of the deal, just eight are openly advocating Brexit. The SNP is backing Remain along with the Liberal Democrats, the SDLP, the UUP, Plaid Cymru and Green MP Caroline Lucas. The only opposition MPs who want Brexit are the eight from the DUP, and Ukip's Douglas Carswell.

But on the benches behind the Prime Minister the split between Leave and Remain is significantly more balanced. The press has lavished attention on Boris Johnson’s decision to support the Leave campaign, but most senior figures have backed the Prime Minister. Just five cabinet ministers (including, notably, Cameron’s longstanding personal friend Michael Gove) and one minister attending cabinet are backing Leave. And plenty of those senior figures backing Cameron have long records of euroscepticism (Philip Hammond, Sajid Javid, Michael Fallon).

Yet there is a broader picture beyond the cabinet room. At the time of writing, more of Cameron’s MPs have declared for Leave than Remain, with 134 supporting In compared to 143 in favour of Out. And 53 are taking even longer than Johnson to get off the fence.

Some of the MPs who have declared for Leave are in particular positions that will cause awkwardness for the government. Over the weekend, several government figures, not least the PM and Theresa May, made the case that membership of the EU keeps the UK safer. But the Minister for Security, John Hayes, clearly doesn’t agree: he’s voting to leave.

The Defence Secretary Michael Fallon was also arguing the national security case for staying in the EU on the BBC's Today programme this morning. But of the four MPs who are junior ministers in his department, two are supporting Brexit and two are undeclared.

And then there’s welfare. A cornerstone of the PM’s deal is the seven-year emergency brake, freezing in-work benefits for EU citizens who come to the UK. The implementation of the brake will be the responsibility of the Department for Work and Pensions. It’s perhaps a bit awkward, then, that three of the four MPs who are ministers in that department are backing Leave. With the fourth's position currently undeclared, it’s possible that any MPs who want to scrutinise the emergency brake proposals at DWP questions in the Commons would be answered by ministers who evidently think them insufficient.

Justice, too, could become a department where every minister in the Commons wants a vote for Leave: as well as Michael Gove, three junior ministers are supporting Brexit and two are undeclared. That could rather undermine Cameron’s plan to assert the UK’s sovereignty with a new law – a project that he has already farmed out to Oliver Letwin in the Cabinet Office.

The departmental breakdown is not all bad news for Cameron. Every single minister at the Department for Business, Innovation and Skills is supporting In, bolstering the business case for staying in the EU.

Whatever the junior ministerial breakdown, the MPs’ declared positions so far imply that the Conservative party is very much on a Eurosceptic trajectory. Of the 74 MPs first elected in May, 25 are backing Leave compared to 21 supporting Remain. 28 are yet to declare, but their prevarication suggests at the very least some sympathy with the case for Brexit.

This only reinforces my colleague George Eaton’s explanation of why Johnson came out for Leave. We know that the Conservative grassroots who will have their final say between two leadership candidates are predominantly supportive of leaving the EU. With so many MPs also supporting Brexit, especially those with much of their careers ahead of them, the Mayor of London has surely also increased his chances of being one of that final pair.