How many votes does Theresa May need to get her deal over the line?

Theresa May has urged MPs to “come together, to back this improved Brexit deal”, maintaining she has secured legal changes to the controversial backstop.

But has she done enough to she reverse the humiliating 230-vote defeat she suffered the last time the Commons passed judgment on her Brexit plan?

There are 634 votes in play, which were split 202 in favour and 432 against on the last vote.

Mrs May needs at least another 116 votes on Tuesday night to reach the necessary 318 votes to give her a much sought-after majority.

Were all Tory and DUP MPs to support her, along with the three independents who backed her last time round, the Prime Minister would have 324 votes – enough to see her just over the line.

But with the DUP’s 10 MPs indicating they will not back the deal in tonight’s vote, the Prime Minister’s total is already down to 314.

She might be able to claw back a majority with a handful of votes from Labour.

This presupposes that all MPs of her own party will back her, however, and this does not look likely.

The European Research Group (ERG) of Tory MPs has urged its members not to support the deal.

They may choose to abstain rather than vote against or cast their vote in different ways.

But just as Mrs May needs 318 votes to be sure of victory so the opposition parties need only 318 votes to be sure of defeating the government.

The combined total of MPs from the SNP, Plaid Cymru, Liberal Democrats, DUP, Greens and the Independent Group, plus the Labour MPs and independents who rejected a deal last time round, comes to 317.

If only one Tory joins them and votes against the deal, the Government will have lost – regardless of how many more Tory MPs abstain.

Perhaps unsurprisingly, Labour leader Jeremy Corbyn has urged MPs to reject the deal.

Shadow Brexit secretary Sir Keir Starmer said he will be surprised if the changes that have been made are sufficient to allow the Attorney General to alter his most recent legal advice.

Prominent Tory backbencher Damian Collins, who backed remaining in the EU in 2016, said he will be voting against the Government’s motion, while former Brexit minister and ERG member Steve Baker said he thinks the deal “falls very far short of what the Government whipped us to vote for”.

Prominent Remain figure Nicky Morgan signalled support for the changes, while Tory pro-European Dominic Grieve said he would vote against the deal.