Parliament does not just split into leavers and remainers. In fact, there are a number of volatile factions that party whips on both sides of the House of Commons will need to navigate when the final Brexit deal is put to a vote. Here are the factors in play:

The Brexit ultras

These Tory MPs and ex-ministers have gone so far down the road of decrying the final deal, it is hard to see how they could back down now. Most prominent are the departed cabinet ministers Boris Johnson and David Davis, the former Brexit minister Steve Baker and the chair of the European Research Group, Jacob Rees-Mogg. In total, 51 MPs have publicly backed StandUp4Brexit, a grassroots campaign that opposes May’s deal, though some may crumble.

Verdict: vote against.

The wavering Brexiters

Not all backbench Brexiters have shown their hands and No 10 will be hoping it can win over some more high-profile MPs to publicly back the deal as a show of strength. After the Chequers deal was revealed, that role went to the Tory party deputy chair, James Cleverly, and Geoffrey Cox, who was made attorney general for his trouble. Will this work again?

Verdict: toss-up.

The ‘Brexit delivery group’

Whatever the noises off, the vast majority of Tory MPs will back the prime minister’s deal, including prominent remainers such as the former home secretary Amber Rudd. Simon Hart, known for his acerbic takedowns of Brexit rebels on Twitter, runs the “Brexit delivery group” of moderate MPs who want to see a deal done.

Verdict: vote in favour.

‘Norway for now’

This small faction is led by the ex-minister Nick Boles, backed by the former education secretary Nicky Morgan and the Labour Brexiter Frank Field. They argue that the deal on offer is less favourable than a Norway-style arrangement, which could serve as a transition towards the negotiation of a free, Canada-style deal.

Verdict: vote in favour, but move if the deal falls.

Tories for a People’s Vote

These are the most committed of Tory remainers. They include the ex-business minister Anna Soubry, the former education secretary Justine Greening and a number of other ex-ministers who have quit over the government’s Brexit position – Phillip Lee, Jo Johnson and Guto Bebb.

Verdict: vote against.

Nervous Tory remainers

Tory remainers who backed rebel amendments to the EU withdrawal bill are not a unified force and many have remained tight-lipped about how they could cast their vote in the face of a potential no deal. Those who have not explicitly backed a second referendum include Stephen Hammond, Jonathan Djanogly and Vicky Ford.

Verdict: toss-up but many could vote in favour, grudgingly.

The Labour frontbench

Jeremy Corbyn and Keir Starmer are highly likely to whip Labour MPs to vote against May’s deal, arguing it does not meet Starmer’s six tests. They will sell it to MPs as a chance for Labour to influence the position and even force a general election. Most MPs will fall into line and vote with the whip.

Verdict: vote against.

Labour for a People’s Vote

This group, including Chuka Umunna, Stephen Doughty and Stella Creasy, have caused trouble for the Labour frontbench in the past by voting in favour of pro-Europe amendments. They will not be a bother this time round as they are fully behind voting down the deal, but will focus their efforts on any potential amendments.

Verdict: vote against.

Could Labour’s Gareth Snell (left), whose constituency voted leave, defy Jeremy Corbyn? Photograph: Joe Giddens/PA

Tricky Labour leave constituencies

Some Labour MPs in leave-voting seats have expressed strong concerns about a potential backlash against their party should Labour be seen to be blocking Brexit. Those concerned include Gareth Snell, Caroline Flint, Lisa Nandy and Laura Smith. Labour whips are convinced many can be convinced to vote against.

Verdict: toss-up.

Veteran Labour Brexiters

There are a handful of Labour MPs who are long-term Brexit supporters but cannot be counted on to support May’s deal. Kate Hoey has said she will not back the PM’s version of Brexit. Others such as Dennis Skinner are close to Corbyn and are unlikely to rebel against him at this late stage. But others could decide they are determined to deliver Brexit.

Verdict: could split, but Corbyn loyalists likely to vote against.

The DUP

The government’s confidence and supply deal with the Democratic Unionist party may end up being the plank upon which this deal depends. So far the DUP MPs are not happy, with Nigel Dodds and Sammy Wilson the deal’s most vocal critics. But government sources are quietly confident they are persuadable.

Verdict: toss-up.

The Lib Dems

The party’s policy is for a second referendum, so MPs should be a nailed-on vote against the deal. But it is worth watching the movements of some of the MPs who have leave-leaning seats, including Norman Lamb and Stephen Lloyd.

Verdict: vote against, for the most part.

The SNP

Probably the most ultra-loyal party in the Commons, as MPs rarely if ever break their party whip. The Scottish National party is set to be a unified front against the Brexit deal put to parliament.

Verdict: vote against.