Vote on Boris Johnson's Brexit deal in Parliament – live updates – CNN International, CNN

Today will absolutely, categorically determine the future of Brexit. Unless it doesn’t.

An amendment to Boris Johnson’s deal has the potential to shake everything up. The measure has been proposed by Oliver Letwin, an MP who was booted out of the Conservative parliamentary party last month when he supported anti no-deal legislation known as the Benn Act.

The amendment says the House would “withhold support” from Johnson’s plan until all of the legislation required to implement the bill is passed by Parliament as well.

It would force Johnson to request a Brexit extension on Saturday night, as per the Benn Act, and remove the risk of no deal in a few days’ time. But it still allows Johnson to pass his Brexit deal – he just has to pass all the separate parts of the Withdrawal Agreement as well.

Nick Boles, who has co-signed the amendment, suggested the vote on the amendment could be read as a political indication of whether the House would support the deal, but not as a legal endorsement of the deal. (Liberal Democrat leader Jo Swinson has also signed the amendment, despite being opposed to Brexit altogether).

What does this mean for Saturday?If Letwin’s amendment passes – and it enjoys support from a cross-section of parties – it would mean that Saturdayisn’tthe be-all-and-end-all. Instead, the subsequent votes on the Withdrawal Agreement in the coming weeks become all-important, because they would need to be approved if the Brexit deal is to come into effect.

What does it mean for Brexit?If the Letwin proposal comes into effect, the government plans to leave the EU by October 31 would be thrown into the air. Such an outcome opens up the possibility that the entire withdrawal agreement could be amended, for example with a requirement to hold a second referendum on the final outcome.

Will it pass?The amendment is signed by members of the three main political parties, including the aforementioned Hilary Benn, and the leader of the Liberal Democrats, Jo Swinson. But everything hinges on whether the Labor leadership decides to swing its entire bloc behind it. The Guardian’s political editor, who is well connected in Labor circles,thinks it might, as doesBloomberg.