If the Commons backs Theresa May’s proposed deal, Britain will at least have some certainty about what the future is likely to hold. Whether it will be happy about it is another matter.
There is no good outcome in this, even if the vote goes the Prime Minister’s way. For the first time in my recollection a Government is trying to get a piece of legislation through that – by its own admission – will make the country worse off than it is now, both economically and in its relations with the EU, the single biggest overseas market Britain has.
That is how skewed the whole issue of Brexit has become. Nobody is really content about the deal, not even Mrs May herself, but however unpalatable it is, perhaps pragmatism will persuade MPs to back it in the hope of making the best of a bad job at some point in the future.
Or perhaps not. Maybe the rebels within the Conservative ranks, and the DUP on which the Government depends, will turn tonight into one of the most catastrophic and humiliating defeats any governing party has ever suffered. It would be a step into the unknown, without precedent.
Mrs May then has three days to come up with a Plan B. Except reality dictates she won’t have three days. If the financial markets are not to go haywire at the prospect of Britain crashing out of the EU with no deal, the Prime Minister will have to say something to calm them if not immediately, then certainly by tomorrow morning.
What that might be is anybody’s guess. What it cannot be is yet another statement from a Premier who lacks flexibility that she is going back to the EU in an attempt to extract further concessions.
That has no credibility any more. She has said it too many times, and been rebuffed too often, for it to be believed at this critical juncture.
There will be a broader question over her credibility to remain in office if she loses badly. But Mrs May doesn’t look like the sort to resign without a struggle.
Call it doggedness or plain stubbornness, but she will hang on if she can.
Whether she is effectively forced out by a coalition of backbenchers of both main parties who hijack the Brexit process using Parliamentary procedure, as was suggested at the weekend, is another matter.
There are those amongst the Conservatives delighted at the prospect of Britain heading towards a no-deal Brexit. That is what the likes of Jacob Rees-Mogg and Iain Duncan Smith have always wanted, despite the warnings of every credible business organisation that it would be potentially disastrous.
But for the rest of the country, a defeat for the Government tonight plunges us all into a limbo under a Prime Minister stymied at every turn. Whatever the politics of her position, she is not a figure who looks able to lead the country out of this mess.
Meanwhile the country drifts towards what looks increasingly like a potential crisis, with exercises being held at Channel ports to plan for massive delays to hauliers carrying goods.
It is a measure of how little grip the Government seems to have that it countenanced the absurdity of giving a multi-million pound transport contract to a ferry company with no ships.
Labour is not helping matters by failing to set out its position. Jeremy Corbyn is woefully vague. Beyond repeating that he wants a general election, and promising to table a vote of no confidence in the Government, there is nothing coherent on offer from the Opposition.
Insisting that a Labour administration could negotiate a better deal with the EU doesn’t hold water, because no detailed proposals have been put forward. The party appears to want power first, and then to worry about Brexit afterwards.
But the electorate is unlikely to vote Labour in unless it hears how the country can be pulled out of the morass that Brexit has become.
It doesn’t seem to occur to Mr Corbyn that he sounds exactly like Tory hardliners such as the former Brexit and Foreign Secretaries, David Davis and Boris Johnson, who are endlessly critical of the Government’s position without advancing other options.
So far, Mrs May has relied on ducking and diving from showdowns, endlessly delaying decisions in the hope of leaving Parliament no option but to back her proposals, however flawed.
This was always a shabby strategy, and never in the best interests of the country. A point was always going to come when the Prime Minister was going to run out of room and time for such manoeuvres.
Tonight would appear to be when that point arrives. And it may also be the point when all the past uncertainty over Brexit pales beside what lies ahead.