May cannot even count on her own bitterly divided Conservative Party colleagues, some of whom are calling for her to step down.
Frustration from across the political spectrum has now erupted into open fury.
Labour Party lawmaker Lisa Nandy, who indicated Wednesday that she might vote in favor of the prime minister’s deal when it next came before Parliament, on Thursday described May's comments as "disgraceful."
“Pitting Parliament against the people in the current environment is dangerous and reckless," Nandy said in a tweet. "It will have cost her support."
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James Gray, a Conservative, called on May to stand down after the vote, which is now expected early next week.
"Why on earth does she want to stay on?" he told NBC’s British partner, Channel 4 News. "She’s the least popular prime minister in the history of prime ministers. Why on earth does she want to stay here? Time she went.”
Others have accused May of even putting lawmakers' lives in danger by telling the public it was Parliament’s fault that Brexit may not happen on March 29 as planned.
“Theresa May knows that MPs across the House are subjected to death threats — some very credible,” opposition Labour lawmaker Wes Streeting tweeted Wednesday. “Her speech was incendiary and irresponsible. If any harm comes to any of us, she will have to accept her share of responsibility.”
Dissatisfaction from within the Palace of Westminster — as the Houses of Parliament are known — echoes the feelings of many across the country. Nine in 10 Britons believe the United Kingdom's handling of negotiations to leave the E.U. is a "national humiliation," according to a poll conducted Sky News and released Wednesday. One in three believe the primary responsibility lies with the U.K. government.
Because of the deep divisions that separate lawmakers, the prime minister's settlement with the European Union has been crushed twice in the House of Commons — suffering the heaviest and fourth heaviest losses in parliamentary history.
Different factions believe that their preferred way out of the chaos — from a second referendum or general election to a so-called soft Brexit and even no Brexit at all — has a chance of coming to pass.
After writing to the E.U. on Wednesday to request a three-month delay to Brexit, May told Britons that Parliament had done "everything possible to avoid making a choice."
Senior European officials have said they will only grant an extension if Parliament votes for a divorce deal.
She must now hope that with time running out, she will be able to persuade lawmakers to back her deal to avoid a “no-deal” exit, which many experts say would be an unprecedented act of economic self-harm.
At the moment, U.K. law says that its membership of the E.U. will end at 11 p.m. March 29, whether there's a deal in place or not.
With European leaders skeptical and parliamentarians angry, crashing out of the E.U. now appears a real possibility.
Saphora Smith is a London-based reporter for NBC News Digital.