Forecasting tight Commons votes on a new measure is a mug’s game – especially a Brexit one like today’s Withdrawal Bill.  There are too many variants, even before one takes into account, as one must, this biased Speaker.

Programme motions, how the parties whip, money resolutions, whether potential rebels turn into real ones, timetabling, unexpected illnesses and absences, Lords Amendments, the inevitable unpleasant surprises in the text of the Bill: all these make events even more unpredictable than they would otherwise be.

All that said, there are only two possible outcomes for Boris Johnson – both today, in the wake of the Bill’s Second Reading; and later, as it moves through the Commons and up to the Lords (assuming this happens in the first place).

They are that it all works out well or badly.  Saying so is obvious; the implications may not be.  And the best place to start pondering them is by musing on the potential reaction of Brussels, Berlin, Paris, Dublin, and the European institutions more widely.

The EU27 has not responded to either of the Prime Minister’s extension letters as we write.  There will be roughly three main dispositions among the various actors.  All will understand very well the difference between what the first (unsigned) letter and the second (signed) one said – and that Johnson’s real view is in the latter.

The first, publicly expressed by Emmanuel Macron, is that the EU and UK should get on with it, and that there should be no further extensions.  This is the most helpful position for the Prime Minister, because it enables him to present a choice to the anti-No Deal Commons: my deal – or no extension and No Deal.

The second is that the EU shouldn’t interfere in the internal politics of member states, a take buttressed by fear of the consequences of No Deal for everyone involved, the economies of the EU states included.  This view seems to be closer to where Angela Merkel is.

The third is an entirely natural one: wait and see.  When on earth will you Brits make up your minds what you want? ask our flummoxed negotiating partners, who have seen the Commons declare itself against: Theresa May’s deal, No Deal, revocation, a second referendum, Commons Market Plus, EEA membership – the lot.

If the Prime Minister has a good day at the office today and later, EU opinion is likely to swing towards a short extension, if any.  The EU will propose a few extra days or weeks to get the Bill through Parliament if necessary, and the UK will at long last leave the EU before the end of the year.

But if he has a bad one, the consensus may swing the other way, particularly given the nervousness among the EU at the prospect of No Deal.  (Who said that it would be a problem for Britain only?)  The likelihood is that a longer extension would be offered – particularly if Johnson has to pull the Bill altogether.

In those circumstances, it is not difficult to imagine the Commons going into a death spiral.  First, the Prime Minister would rightly demand a general election.  Thanks to the genius of Oliver Letwin, inter alia, he can’t just go to the Palace and ask for one: he is bound by the Fixed Terms Parliament Act.

In a nutshell, this makes the gaining of the requisite two-thirds majority necessary for an election to be called impossible without the support of the Labour Party.  Which may be a turkey, but if so is one that can read the polls, and won’t vote for Christmas.

Instead, John McDonnell and Keir Starmer, the duopoly that seems to run Labour’s Brexit policy these days, would doubtless throw its collective weight behind a second referendum.  But it is very doubtful whether the Commons is any better disposed to approving a second plebiscite than it is to approving anything else.

After its supporters had had a few goes at getting one – the Speaker would presumably waive his strictures against repeated motions – the logical consequence would be an election.  However, there’s no reason to think that pushing a second referendum would boost Labour’s ratings outside London, some other cities, and their hinterland.

At which point, the spiral would twist further downwards.  ConservativeHome is pro-MPs (it is unlikely to be otherwise, since it’s edited by someone who was one).  It believes that most work very hard for their constituents and the country in circumstances increasingly unfavourable to entering public life.

And they have gradually hauled their reputation off the floor to which the expenses scandal took it.  On balance, having governments with small majorities or none has been good for the legislature: backbenchers have had more of a chance to leave their stamp on events.

But the reputation of MPs wouldn’t be enhanced if they were only doing half their job: that’s to say, their constituency work.  Ultimately, voters want governments to govern, and that means decisions, Bills, votes, Acts, and the measures that follow.

If MPs are unwilling either to faciltate this Parliamentary normality, or else help an election to happen, they will be drawing their taxpayer-funded salaries and expenses for not very much.  Their constituents will notice, and the Commons’ reputation will suffer.  In short, they would become like the welfare scroungers of tabloid legend.

So quite apart from the merits or otherwise of the Bill, they have a collective interest in passing it in good time – whatever one thinks about the precise timetabling.  We hope they will bear this in mind when they come to vote later today.

As for the Bill itself, it proposes a deal which isn’t perfect but which, because it offers a route to a free trade agreement, is better than the last one.  The alternative is likely to be a second referendum or an unpredictable election.  Brexiteers thus have a bird in the hand – and it’s better than than either of these other two in a bush.

It was said that Boris Johnson wouldn’t get a new deal, but he did.  That he wouldn’t get rid of the backstop, but he did.  That the EU would never change the Withdrawal Agreement, but it did.  That it would trap us in the Customs Union: but a particular merit of the deal is that it offers the whole UK an exit route.

Voters are fed up with delay, procrastination, dithering – and Professor Branestawn-type spinning machine of procedural Letwinism.  MPs shouldn’t allow a gulf to open up between themselves and those who elect them.  They can begin to close it by backing this Bil..