The UK Prime Minister is under mounting pressure to ditch the Irish backstop, with two months to go until Brexit D-Day.
Her former foreign secretary Boris Johnson says she'll have the 'full-throated support' of the nation if she renegotiates it with the EU.
Writing in the Telegraph newspaper on Monday, the pro-Brexit Conservative lawmaker says if May gets the 'freedom clause' from the backstop she's reportedly seeking, it'll be 'unadulterated good Brexit news' for Britain.
The backstop's designed to make sure there's no return of a hard border between Northern Ireland and the Republic of Ireland if no deal is in place by the end of the Brexit transition period.
That means no checkpoints, no border posts, no barriers.... but at the cost of the UK staying in the EU customs union during that time, without any power in its decision-making, and Northern Ireland having to stick to more EU trading rules: a cost many lawmakers say is too great, despite Ireland's insistence it won't accept any changes to the backstop.
The EU, too - with its deputy chief negotiator repeating on Monday (January 28) that the bloc won't be negotiating on the divorce deal
It's one of the main reasons they rejected May's deal in parliament earlier this month, and the focus of a number of the amendments to the deal they've tabled since that vote, that also include efforts to delay the UK's exit day past March 29th.
Those amendments will be voted on in parliament on Tuesday (January 29), and if one is passed it could be the lifeline May's deal needs to pass itself.