This week’s big news, overshadowing Brexit for once, is the split in both the Labour and Conservative parties. Nine former Labour MPs and three Conservatives, have so far quit their parties, mostly sitting together in the House of Commons as ‘the Independent Group’. How significant is this for British politics? Could it be the start of a major realignment of the parties, or is simply a last splutter of the politics of the ‘failed status quo’?  Like the French Revolution, it is too early to tell. But both main parties, which are increasingly defined by economically risky ideological projects of the formerly marginal right and left, will be worried that MPs have chosen to quit, blaming political extremism in their former parties and making a claim for the centre ground. The leadership of both government and opposition need to negotiate with centrist MPs in order to deliver Brexit, an election, or other priorities in a hung Parliament. That is likely to remain true after the next election.

While the long-term effects are uncertain, the party splits will have an effect on two major questions: immediately, by pressurising No10’s Brexit strategy of taking the Parliamentary meaningful vote to the wire. And, in slower time, on the chances of an election this year.

What unites the newly independent MPs is opposition to Brexit. Within the Conservatives, the split strengthens Remain-inclined MPs who are opposed to risking no deal. They can credibly threaten to leave if Mrs May does not commit next week to seeking an extension of the Article 50 process; rebelling to pass the Cooper-Letwin amendment next Thursday would be a clunkier way of achieving the same end. No10 are worried; they must either risk defeat, and so lose control of the process, or bring forward a meaningful vote on Mrs May’s deal without any major concessions from the EU – which would almost certainly be defeated a second time, perhaps fatally. Their only other option is to cave in to pressure, as has happened so often before, though usually from the ERG, and commit to seeking an art.50 extension if a deal has not been approved by a point early in March. Some in the ERG still hope to engineer a no deal Brexit; a government concession or defeat on process next week would confront them with accepting the current deal, seeing it soften, or Brexit being delayed. While that might ultimately help Mrs May pass her deal, it makes it harder to hold the Tories together.

For Labour, too, the split strengthens the position of the MPs in the party calling for leadership support for a new referendum. They also have the advantage of numbers within the Parliamentary Labour Party, and perhaps a feeling that they have little to lose under Jeremy Corbyn’s leadership.

For both party leaderships, therefore, the splits increase the pressure to get a withdrawal agreement passed and Brexit defused as an immediate issue, if this is at all possible.

There is a further reason for that. British politics has under-priced the fact that any extension of Article 50 will probably come with conditions. The short extension (two to three months) that most MPs imagine to be easily deliverable on request is only likely if the Commons passes a deal before 29 March. If not, the EU may only offer a much longer extension (one to two years). This may be just a  negotiating tactic, to focus Westminster minds, but it has a logic; EU27 governments are sick of Brexit and want the UK to make a choice. The other leaders also don’t have to come back to this every few months.  An extension will not remove the negotiating pressure to sign up to a deal.

Finally, the splits make an election this year more likely, for the simple reason that it becomes even harder for the government to put a majority together again after passing a deal which the DUP and some of ERG are likely to oppose strongly. Few MPs, not least those who have just quit their old parties, may want an election imminently. But it is getting harder to see, post-Brexit, how anyone can govern effectively through to 2022 without one.