Can Johnson pass his Brexit deal through the House of Commons?

Related: Boris Johnson and EU reach Brexit deal without DUP backing

Boris Johnson faces an uphill battle to pass his Brexit deal through the House of Commons without the support of the DUP. It would be just about doable if he retained all MPs who voted for the deal last time, all of the 28 Eurosceptic “Spartans” who rejected Theresa May’s agreement, and won over a handful of Labour MPs.

However, there are jitters about the deal among Eurosceptics, expelled former Tories and pro-deal Labour factions, making the result extremely uncertain. The prime minister has about 259 votes in the bag, and needs another 60-odd to get over the line (depending on abstentions). There is a possible pool of approximately 71 votes:

European Research Group (28)

This group of hardline Brexiters are reserving judgment until they have fully examined the legal text of the UK-EU agreement. It would be hard for many of them to back a deal rejected by the DUP.

Johnson has worked hard at trying to get them on side, promoting leading hardliners such as Priti Patel and Theresa Villiers to his cabinet. He has held meetings with them throughout the process of getting a deal, keeping them informed. But they would not vote for an agreement until they were sure the legal text matched what he has promised them.

Patel, Villiers, Andrea Jenkyns, Ranil Jayawardena, Lee Rowley and James Duddridge have so far all indicated they are likely to be on board. That still leaves 22 votes to win.

Steve Baker, the chair of the European Research Group, said he was optimistic about supporting a “tolerable” deal but he has not given his blessing yet. There will be a meeting of the ERG to decide on how they should vote, possibly on Saturday morning.

Former Tory anti-no-deal rebels (19)

This group of expelled Tories – who had the whip withdrawn for trying to block a no-deal Brexit – originally numbered 21 but Sam Gyimah has since joined the Liberal Democrats. Three of them – Justine Greening, Dominic Grieve and Guto Bebb – will vote against a deal because they want a second referendum. But it makes sense to add in Nick Boles, who is an independent and voted for a deal last time, and Amber Rudd, who resigned in solidarity with her colleagues. Bringing the number of possible votes from former Tories to 19.

These ex-Conservatives are mixed on whether they would now back a deal. Most of them would probably support Johnson because it would avoid the UK crashing out with no deal. However, there is some concern among former cabinet ministers such as Philip Hammond and David Gauke that the deal is far harder than they would have wanted. Another of those expelled, Margot James, told the BBC she was likely to give a Johnson deal the “benefit of the doubt”, but she felt his current proposal was worse than May’s.

Pro-deal opposition MPs (21)

There are 19 Labour MPs who indicated to the EU that they could be willing to vote for a deal if it contained sufficient assurances on protecting workers’ rights, the environment and giving parliament a say on the future relationship. Out of their number, four Labour MPs already voted for the deal last time, plus another one who didn’t sign it, John Mann.

Counties and customs

Inside the EU, both Ireland and Northern Ireland are part of the single market and customs union so share the same regulations and standards, allowing a soft or invisible border between the two.

Britain’s exit from the EU – taking Northern Ireland with it – risks a return to a hard or policed border. The only way to avoid this post-Brexit is for regulations on both sides to remain more or less the same in key areas including food, animal welfare, medicines and product safety.

The 'backstop' in Theresa May's Withdrawal Agreement was intended to address this - stating that if no future trade agreement could be reached between the EU and the UK, then rules and regulations would stay as they are. This has been rejected by Brexit supporters as a 'trap' to keep the UK in the EU's customs union, which would prevent the UK striking its own independent trade deals.

There are an estimated 72m road vehicle crossings a year between Northern Ireland and the Republic of Ireland, and about 14% of those crossings are consignments of goods, some of which may cross the border several times before they reach a consumer. Brexit supporters say this can be managed by doing checks on goods away from the border, but critics say it will be difficult to police this without any physical infrastructure like border posts or cameras, which could raise tensions in the divided communities of Ireland.

Interactive: A typical hour in the life of the Irish border

They would come under huge pressure from colleagues not to sign up for a Johnson-led deal but a few may break with their party. Labour has indicated they probably would not lose the whip if they voted with the government. Norman Lamb, a Liberal Democrat who is standing down at the next election, has also signalled he could be willing to vote for a deal.

Independents (4)

Related: Corbyn refuses to confirm backing for second referendum on Johnson's deal

There are four independents who voted for May’s deal last time – Ian Austin, Sylvia Hermon, Frank Field and Stephen Lloyd. Will they do the same again?

Boris Johnson’s brother (1)

Jo Johnson voted against May’s deal three times because he wanted a second referendum. He later joined his brother’s cabinet, signing up largely to its Brexit policy, but then resigned saying he was “torn between family and national interest”. His vote would be crucial as to whether he goes for a Johnson deal or sticks to his guns on a second referendum.

A note on abstentions

If it goes down to the wire, it could be incredibly important to see who abstains. Last time, Dennis Skinner, Kelvin Hopkins and Ronnie Campbell – three veteran Lexiters – were all absent. But would they take a different view on a Johnson-backed deal and vote against?