After Theresa May's defeat, the options may be no-deal or general election
Maybe I am simply in the thrall of the powerful emotions manifested by MPs in their debate on Friday, but their rejection of the Withdrawal Agreement just now feels the most significant event to date on the long and tortuous road to Brexit or revocation.
Because the EU just a week ago bent its rules to accommodate the prime minister's request for a modest Brexit delay, and also tried to make it easier for her to ratify the deal by saying only the divorce part - the Withdrawal Agreement - would need MPs' approval to secure a postponed Brexit date of May 22 for leaving the EU.
Parliament has thrown the compromise offered by the EU's 27 leaders back in their faces.
That is why the president of the EU commission Jean-Claude Juncker and its Chief Negotiator Michel Barnier have just said that "a no-deal scenario on April 12 is a likely scenario", for which the EU is "fully prepared".
Lots of MPs see that as posturing, somehow an attempt by the EU to bully the UK into accepting a long Brexit delay or no Brexit at all.
That is wrong, and perhaps dangerously so; the EU's 27 leaders want to be liberated from what they feel as the cancerous Brexit uncertainties, that make it impossible for them to rehabilitate their cherished project, and crystallising no-deal is for them a decreasingly scary way of doing that.
As for the prime minister, she described "the implications" of this third humiliating rejection of her painstakingly negotiated plan as "very grave" - and she also said that "I fear we are reaching the limits of this process in this House".
What did Theresa May mean, and what next?
Well, on Monday MPs will hold round two of the Letwin process of trying to find a route through this mess that would be supported by a majority of MPs.
There is a chance that Ken Clarke's motion, for the UK to participate permanently in a customs union, could deliver that majority.
Were that to happen, it could be followed as soon as Wednesday by Mrs May holding yet another vote on her deal, this time with a customs union condition bolted on, just in case such a reworked Brexit package could at the last see the Withdrawal Agreement ratified by MPs.
There is a smaller probability that the Beckett/Kyle/Wilson proposal of a confirmatory referendum, for any Brexit supported by the Commons, could win the Letwin beauty parade - though I would bet little on that.
The hope of some MPs, that a hybrid of Thursday's motions - Clarke crossed with Beckett for example - could be a winner, looks a naive and futile exercise in political interbreeding.
That said, if MPs do show support for a credible route to avoid no deal - such as Clarke's customs-union proposal - that would presumably be embraced both by May and the EU. And a smoother negotiated Brexit would be back on.
If they don't, we are leaving without a deal in a fortnight - which is presumably why the president of the EU council Donald Tusk has convened an emergency council of EU leaders on April 10.
Is there an emergency cord to pull, should we find ourselves hours from no deal?
It is possible MPs may collectively vote to turn the Brexit default from no-deal to revocation.
The SNP believe Labour is coming round to this idea - though even if Corbyn supports it, passing a motion that would mandate the PM to cancel Brexit rather than leave without a deal could cause the mother of all constitutional crises, since Mrs May has consistently said she would never revoke.
That said, the orthodox meaning of what the PM said, of the Commons having almost exhausted "the limits" of trying to deliver on the historic referendum decision, would be that the Commons should be dissolved, that there should be a general election.
Theresa May really doesn't want that, according to her officials.
But equally one of her closest ministers told me the risk of going to the country is exceptionally high - especially since the EU has said it would allow a further Brexit delay if the Brexit preferences of the UK needed to be tested again in an election.
At least after Friday Mrs May has a Brexit policy to put in an election manifesto, since 90% of her MPs voted for the Withdrawal Agreement - and when I mentioned to a Tory official that Friday's defeat had yielded that advantage for the PM, I was greeted with a giggled "we're all getting ahead of ourselves" rather than a denial.
Consider yourselves warned.