Theresa May's fate looked sealed after the resignation late Wednesday following the resignation of Cabinet minister Andrea Leadsom, who quit saying she could not support the EU withdrawal bill that May plans to introduce to Parliament.
Leadsom, as leader of the House of Commons, had been due to announce Thursday when a vote on the bill would be held.
However, she said she could not support May's Brexit plan because it did not "deliver on the referendum result" that saw voters in 2016 opt to leave the EU.
"No one has wanted you to succeed more than I have, but I do now urge you to make the right decisions in the interests of the country, this government and our party," Leadsom wrote in a resignation letter to May.
Beware the Ides of May
This comes as a growing number of Conservative lawmakers have been calling on May to resign. The party's legislators want May to agree by this Friday that she will quit, triggering a Conservative leadership contest.
If not, they are likely to try to topple her.
May became prime minister soon after the June 2016 EU membership referendum, and has spent her entire term in office trying to deliver on that decision.
She seemed to come close to success when she struck a divorce agreement with the EU late last year. But lawmakers have rejected it three times, and Britain's long-scheduled departure date of March 29th passed with the country still within the bloc.
Many Conservatives blame May for the delay, and believe she is now an obstacle to Brexit. They want her replaced with a more ardent Brexiteer such as the former foreign secretary Boris Johnson.
May maintains another leader will not be able to strike a better deal with the EU. On Wednesday she urged lawmakers to support her Brexit bill, saying that if they reject it "all we have before us is division and deadlock."
If Theresa May stays on until next week, pressure is likely to increase when results come in from this week's elections for the European Parliament, with Conservatives expect to receive a drubbing.
Many British voters on both sides of the Brexit debate look set to use the election to the EU legislature to express displeasure over the political gridlock. Opinion polls show strong support for the single-issue Brexit Party largely from angry former Conservative voters and for pro-EU parties including the Liberal Democrats and the Greens.
The election is being held today in Britain, but results won't be announced until all 28 EU countries have finished voting by late Sunday.
UK media: It's the end.
British newspapers on Thursday were unanimous in declaring the end is nigh for May.
The pro-Conservative Daily Telegraph said in an editorial that "either Mrs. May must go as soon as humanly possible, or the Conservative Party must finally remove her."
The Daily Mail, which has been supportive of May, said that "despite her valiant efforts to deliver an honorable Brexit, she has finally run out of road."