Theresa May stood up in the House of Commons at 5:46 p.m. Tuesday to formally begin a weeklong Brexit debate that will culminate in a vote to ratify — or reject — the Brexit deal she agreed with Brussels last month.

By then she had already been upstaged.

Minutes earlier, opposition parties and Conservative rebels defeated the government in a vote to give parliament more power to shape the contingency plan that will be needed if that vote is lost — and current numbers suggest it will be. It wasn’t even the first defeat of the day.

Whatever path Britain takes out of the Brexit quagmire, it is no longer up to the prime minister. Tuesday’s defeats for the government in the House of Commons show May can no longer command a majority on Brexit and lawmakers wielded their power to ensure they are able to force the government’s hand.

In a crowded House of Commons, May looked isolated as she made a final plea for her deal.

An hour before May got to her feet MPs declared the government in contempt of parliament because of its refusal to publish the full legal advice it has received on the Brexit Withdrawal Agreement. May’s administration promptly said it would publish the advice to avoid the unprecedented spectacle of ministers potentially being suspended from parliament.

The threat of such a severe punishment reflects parliament’s sovereign role in the U.K. political system; a sovereign role it is now asserting — with potentially dramatic consequences for Brexit.

‘What forces would it unleash?’

In a crowded House of Commons, May looked isolated as she made a final plea for her deal. If the vote is lost, she will face calls from Labour to resign — and it was possible to discern a valedictory tone in her statement.

To Brexiteers, she said there is no alternative deal to negotiate (“don’t let anyone here think that there is a better deal to be won by shouting louder”); to Labour, she said they are playing politics with their call for a general election; and to those MPs recommending a second referendum, she warned darkly about the “forces it would unleash.”

For the past two years, May has seen her role as a check on populist extremists — “the politics of division and despair” as she called it in a January 2017 speech. She sees her Brexit deal in a similar light. She told Brexiteers that failing to compromise and remain close to the EU economically would be “completely ignoring the views of the 48 percent” who backed Remain.

“Think what it would say to the 52 percent” who backed Leave, she told Remainers pushing for a reversal of the referendum result.

“What it would say about the state of our democracy if the biggest vote in our history were to be rerun because a majority in this House didn’t like the outcome? And what would it do to that democracy, what forces it would unleash?”

As Cabinet ministers sat stony-faced on the front bench, May told MPs the British people want the government to “get on with a deal that … allows us to come together again as a country.”

“We cannot afford to spend the next decade as a country going round in circles on the question of our relationship with the EU,” she said. “We have already spent too many years with divisions on Europe simmering in the body politic.”

But it is no longer up to the prime minister. Twenty-six of her own MPs voted with Tory rebel Dominic Grieve, who put forward the amendment calling for parliament to have a greater say in Brexit planning. On the contempt vote, Northern Ireland’s Democratic Unionist Party, whose 10 MPs guarantee May’s parliamentary majority, voted with the opposition.

If the deal is voted down at the first time of asking on December 11, May has 21 days to set out her plan of action in a statement to MPs.

If May’s Brexit deal is rejected next week, the default next option is a no-deal exit. But such an outcome does not have majority support in parliament. Although the British system means parliament can only express its view or veto government action, rather than take executive power, Tuesday’s events show the lengths to which Tory rebels and the DUP are prepared to go to change the government’s course.

It’s now more likely than ever that the only way forward is one supported by parliament — whether it’s an attempt to renegotiate with Brussels (as fruitless as that seems), a general election forced by a successful vote of no confidence (as Labour has threatened), or a second referendum on EU membership.

Greater power for MPs

While the contempt vote was the most surprising of the day, it was the later vote on Grieve’s amendment that could prove the most significant. It ensures MPs can amend any motion the government brings to the House of Commons relating to its divorce deal with the European Union.

This could prove important as soon as next week. If the deal is voted down at the first time of asking on December 11, May has 21 days to set out her plan of action in a statement to MPs.

Until now it had not been clear whether that could be amended by parliament. Now we know that it can be.

While it is unlikely any such future amendments would be legally binding on the government, they would have great political force and May would face the risk of a vote of no confidence if she ignores them.

Notably, some of May’s former allies, including ex-Cabinet minister Michael Fallon and Damian Green were among the more than two dozen Tories voting with Grieve.

Not that the contempt vote will necessarily be without consequences. Leader of the House of Commons Andrea Leadsom said the government would respond formally on Wednesday, amid demands from the opposition for the legal advice to be published in full before next week’s big vote.

It is difficult to imagine what it could reveal that would damage May’s position any more than it has already been.