It can be a baffling and challenging story to follow and it is about to get even more complicated after Parliament's meaningful vote on Tuesday evening. STV's Political Editor Bernard Ponsonby explains what is at stake, considers what happens next and offers a personal view on some of the key dynamics that will dominate the news in the coming weeks.

THE MEANINGFUL VOTE

This term reflects the fact that agreeing a deal with the European Union is a matter for Parliament as a whole and not just Theresa May and her Cabinet colleagues. In our system of Government Parliament is supreme, the House of Commons is sovereign and ultimately it will be up to all 650 MPs to decide what happens next.

OPTIONS FOR PARLIAMENT

MPs could agree to Theresa May's deal and the UK would leave the European Union on the 29th of March at 11pm.

Alternatively it could be voted down. As a result of a vote in the Commons last week the Government would have three working days to indicate what it intends to do next.

It is likely that the process will be put into limbo as the indications are that the Government's deal will be rejected but it also likely that MPs will rule out leaving without any deal at all. That begs the question, what happens then?

WHAT HAPPENS NEXT?

If there is a parliamentary impasse, something will have to emerge otherwise the UK will crash out of the EU in March.

The Government have insisted the current deal is the only game in town. Mrs May might want to go back to EU Leaders to seek changes to the withdrawal agreement to get more MPs onside if she chooses to put the deal before MPs a second time. The reality is that this is mission impossible for two reasons. First, EU leaders have made it clear they will not renegotiate and secondly the deal would only have a chance of success if the withdrawal agreement is rewritten or changed completely in relation to the customs arrangements in Northern Ireland.

Parliament could give the Government some new 'red lines'. For example it could say go back and negotiate membership of the customs union and single market (the Scottish Government's preferred position if Brexit is to happen). But you are back to the same problem, the EU have said the negotiations are at an end.

If Parliament decides it needs more time to decide what it should do the Government could request an extension of the Article 50 process. This would involve a dramatic u-turn from the Government since Mrs May has insisted repeatedly that this will not happen. It would also require the agreement of the other 27 EU countries.

Is extending Article 50 realistic? On the face of it no, as both the UK Government and EU leaders have said no to this. But politics is the art of the possible. In order to prevent a No deal scenario the Prime Minister might have to consider this. If the mood music at Westminster suggests Parliament is likely to countenance a new deal that would involve closer economic cooperation and perhaps involving the retention of freedom of movement, EU Leaders might just sanction this since such an arrangement would be advantageous to them not least since it is likely to involve future payments from the UK to the EU budget.

Parliament could revoke Article 50 unilaterally and call the whole Brexit process off. No one is seriously suggesting this since it would involve MPs effectively ignoring the result of the 2016 referendum. Strictly speaking all referenda are advisory, they can technically be ignored by Parliament but in reality politicians regard them as politically binding.

A VOTE OF NO CONFIDENCE

At some stage, perhaps in a matter of days, Labour will table a vote of no confidence in the Government. This is not likely to pass since the Democratic Unionist Party has pledged to support the Government in such a vote.

Labour champion this line of opposition as it could lead to a General Election if the Government loses such a vote. Labour's position has not been a model of clarity for a number of reasons. Most Labour MPs don't want to see Brexit happen but are cautious about trying to overtly derail it since many heartland Labour areas voted for Brexit. They judge a political price would be paid for being seen to want to bin the referendum result.

This strategy is not without risk for Labour. If they did get a General Election, the vote would be a Brexit poll by proxy and Labour would have to decide what it would campaign on. Most MPs and a good deal of the membership are at odds with the long held Euro scepticism of the party leader Jeremy Corbyn. A General Election could do Labour more harm than good.

A SECOND REFERENDUM

If Parliament simply cannot decide what it wants the arguments will grow for a second referendum as a means of breaking the log jam.

For that to happen a number of things would have to occur. Article 50 would have to be extended to allow for time to pass an Act of Parliament paving the way for a second poll. My judgement would be that in these circumstances EU Leaders will agree to an extension since it opens the possibility of reversing the original result.

MPs would have to amend the leaving date of the 29th of March by passing what is known as a statutory instrument to remove the leaving date from legislation already passed.

Legal and constitutional scholars reckon legislation on a second poll would take a minimum of five to six months so any new referendum would come in the second half of the year.

The electoral commission would have to agree on the question or option that would be put in a second vote. The cardinal rule in a referendum is that it has to be clear what people have decided, so the idea of a multi option referendum (Remain versus the Government's deal versus No deal) would not be sanctioned since it opens up the possibility of a three-way split where it is not possible to determine what there is majority support for.

A poll where the choice is between Remain and Mrs May's deal would enrage hardline Brexiters. A choice of Mrs May's deal or no deal would enrage Remainers. And a choice of Remain against no deal would not be supported by the Government.

COMMENTARY

A veteran Ulster journalist told me last week that he had a grip of what was coming out the tortuous Northern Ireland peace process during Tony Blair's Premiership but that he simply couldn't read what will happen in the coming weeks. I agree, I simply don't know what will happen either.

As for speculation, I offer the following scenarios as possible if not likely. Mrs May's deal is dead, it simply won't pass. She will inevitably have to consider her position if Parliament foists on her a new negotiating hand that she doesn't agree with.

The EU instinctively won't want to extend Article 50 but in my view will sanction it if it leads to a deal involving closer economic ties or if Parliament goes down the road of a second vote.

The Government will survive even if there has to be a big question over the Prime Minister's position.

I expect the term 'national interest' to become a parliamentary dictum and it might be, aghast at the prospect of crashing out, that cross party initiatives allow Parliament to come to a view that at least can command a majority position. That would in all likelihood involve even closer economic ties than the current withdrawal agreement allows for which would seriously question whether the referendum result was being honoured.

All of this will be played out amid procedural wrangles and a febrile political atmosphere the likes of which we haven't seen before.