We always said that the Brexit negotiations would go to the wire despite there being a two-year timeline.
The Strasbourg meeting on the night of Monday, 11 March, when the UK and the EU tabled various documents may or may not be enough to get the House of Commons to approve the draft Withdrawal Agreement. The EU documents are available here while the UK ones are available here.
There was just enough in the new documents for the doubters to change their mind but there was also just enough lacking in those documents to enable them to vote against it.
The tipping point may now be the UK Attorney General's second opinion on 12 March. His opinion contains both a positive message (from the Prime Minister's perspective in terms of securing approval in the House of Commons):
"I now consider that the legally binding provisions of the Joint Instrument and the content of the Unilateral Declaration reduce the risk that the United Kingdom could be indefinitely and involuntarily detained within the Protocol’s provisions at least in so far as that situation had been brought about by the bad faith or want of best endeavours of the EU"
but also a negative one:
"However, the legal risk remains unchanged that if through no such demonstrable failure of either party, but simply because of intractable differences, that situation does arise, the United Kingdom would have, at least while the fundamental circumstances remained the same, no internationally lawful means of exiting the Protocol’s arrangements, save by agreement."
Ultimately, he says that there is still legal uncertainty. One gets the sense that had his view been more positive, that the deal could have been approved by the House of Commons.
Is that it? Not necessarily. There may well be another attempt by the UK to get further concessions at the European Council Summit on 21-22 March and even last minute talks right up to (and after) the 29 March cannot be ruled out. An extension is possible but the UK has to ask and the EU 27 have to be willing to grant it. The EU 27's unanimous consent is not a foregone conclusion.
Moreover, setting the length of the extension is very difficult – too short won't be enough and too long would be too complicated (e.g., the European Parliamentary elections). The only certainty still is that the uncertainty will continue for a little longer..