John Bercow, speaker of the House of Commons, during an address at Westminster Hall inside the Palace of Westminster in London on March 22, 2018. (Alastair Grant/AP)

Last week’s Parliamentary defeat for the Brexit deal has just been followed by another major event. The Parliament’s speaker has ruled that the government cannot introduce the Brexit deal for another vote, citing a House of Commons precedent that MPs can’t be asked to vote again on a measure in the same parliamentary session.

That could be a problem for Theresa May’s government. It cannot readily change the measure without renegotiating the deal, which the European Union has made clear is extremely unlikely. Speaker John Bercow could decide that if the government and the E.U. agree on either a long extension or a change in the Brexit date, that would change what MPs are being asked to vote on. Or MPs could rewrite these rules entirely.

Outsiders may be forgiven for seeing this — and other legislative maneuvers — as a parliamentary pantomime. But it’s more than a joke. Long-standing rules that have allowed the Parliament to function effectively appear to be eroding.

The Parliament used to be based on clear divisions

Parliament’s physical design — two rows of seats opposing each other — enforces a sharp division between the government’s MPs and those of the opposition and enhances the bonds among party members. Both are being eroded as Britain attempts to leave the European Union. May’s Brexit deal has suffered the two biggest legislative defeats since 1924 — by 230 votes in January and 149 in March. Brexit proponents once described it as taking back sovereignty from Brussels bureaucracy. Now U.K. observers increasingly talk about it as the event that broke the Westminster system.

The question is whether it can repair itself.

The speaker supposedly acts as a referee

The rule book for British parliamentary politics is written by the speaker and the party whips. Here’s how the system works. Members of the House of Commons elect the speaker in a secret ballot. In theory, the speaker is an apolitical, nonpartisan referee for discussion and votes. The speaker decides what Parliament votes on, what measures are selected to be called for debate and in what order decisions are made. Those decisions can have enormous consequences.

Throughout Brexit, Bercow has clearly sought to empower the MPs at large while remaining sensitive to government prerogative — even when his clerks advise that his decisions run contrary to parliamentary convention. For instance, in January he judged, against official advice, that a government motion on its progress in Brexit talks was “amendable.” MPs duly amended it. The way this was done forced the government to come back with a plan three days after losing a vote on its Brexit deal, rather than three weeks later, as it had planned.

Now, by using his discretion to deny the government the ability to put its Brexit deal to parliament for a third or fourth time, some are arguing the speaker has made his politics explicit. The speaker usually declares the winner; now, he is arguably picking it.

The party whips usually keep MPs in line

Meanwhile, each party’s whips make promises and threaten punishment to MPs who don’t vote the right way on key bills. Unlike in the United States, British whips can set a clear party line on a given bill; if you vote against your party on a so-called three-line-whip issue, you are liable to face serious disciplinary action.

But Brexit is stretching traditional party loyalties to the limit. Parliament’s newly created Independent Group is composed of 11 MPs who have left the Conservative and Labour parties, primarily because they oppose Brexit.

Over the last week, the whipping system has seemed on the brink of collapse. Thirteen government ministers from the Conservative Party ignored a three-line whip, rebelling against the idea that a no-deal Brexit should be kept as a live possibility. The next day, Brexit Minister Stephen Barclay announced that it was “time for this House to act in the national interest” and back an extension. He then voted against the very delay he had spoken in favor of.

The unspoken assumption that the government acts as a coherent body and can only stay in office with the support of the House of Commons is starting to crack.

That said, both parties are still trying to shore up MPs’ loyalty. The Brexit deal that Labour opposes is not that different from the deal that it demands. Meanwhile, Conservative MPs have coalesced around a compromise that stood no chance of being approved by the E.U., just to secure party unity. Partisanship remains key to understanding British politics.

Instead of two major groups you have four

There are now four groups in Parliament, each with a different preferred outcome: May’s unpopular deal; a disruptive no-deal Brexit; an as-yet-not-clearly-defined different deal; or, perhaps least likely, no Brexit at all. Only one of these groups will get what it wants.

If allowed another vote on the negotiated deal, the prime minister needs to swing at least 75 MPs from opposing to supporting her plan. She is trying to persuade those who want a no-deal Brexit to back her deal by threatening that E.U. negotiations could go on so long that there would be no Brexit at all. And she will need to persuade Northern Ireland’s Democratic Unionist Party’s 10 MPs, who she hopes will not want to force a snap election that would deprive them of their power over May’s minority government. All this might bring another 50 or so Conservatives to her side.

Then, May would need some Labour MPs to vote her way. Within Labour, those who want another referendum are fighting with others, including Jeremy Corbyn, who would prefer a different Brexit deal. But even the latter don’t want to vote for the Conservative Party’s Brexit deal unless they are sure that this will push May over the line.

Both May and Corbyn want to hold their parties together above all else. That, at least, is normal for British politics. Both leaders are also united, for different reasons, in wanting Brexit to be over and done with. On that at least, they are broadly in agreement with the British public.

Anand Menon (@AnandMenon1) is professor of European politics and foreign affairs, and director of The UK in a Changing Europe, King’s College London.

Alan Wager (@DrAlanWager) is a research associate at The UK in a Changing Europe, King’s College London.