Tony Blair has always wanted to be remembered as a Prime Minister who not only won elections but also transformed the political landscape. The ambition was instilled in him by his mentor and adviser, the late Lord Jenkins, who told him: "Great Prime Ministers change the weather."
In their regular talks while he was Leader of the Opposition, Mr Blair resolved to "change the weather" on two fronts - by realigning Britain's centre-left parties and by resolving Britain's ambivalent relationship with Europe.
As I explained here last week, the ailing Blair project to forge an anti-Tory alliance was killed in the cross-fire between Labour and the Liberal Democrats at the general election. The next 48 hours will probably decide whether Mr Blair can leave behind a positive legacy on Europe.
Until Wednesday, the Prime Minister had always believed that France would vote "yes" in tomorrow's referendum on the European Union constitution. He changed his mind when two opinion polls put the "no" camp on 54 per cent of the vote.
Mr Blair is good at keeping his options open over events beyond his control, as he did during the race between George Bush and John Kerry. Even his closest aides say they don't know whether he would prefer France to vote "yes" or "no".
A "yes" would force Mr Blair to launch the campaign to sell Europe to Britain he has repeatedly postponed since 1997. He believes that the referendum he promised last year and has pencilled in for a year from now, could be won - contrary to the opinion polls and prevailing political wisdom.
Unlike the well-funded "no" campaign, there is not even an embryonic "yes" camp in Britain. No one would stump up the money before the election and the French referendum. So things would have to happen pretty quickly if France approved the treaty.
A referendum in Britain now looks unlikely, despite Mr Blair's promise to hold one even if another EU country voted "no". When the Cabinet discussed Europe on Thursday, the mood was clear: if the French people reject the constitution, a "no" vote in the Netherlands next Wednesday would be inevitable too. So, ministers believe, the constitution would be dead. Mr Blair may virtually pronounce it so on Monday.
It seems that Europe is heading for a bitter split about how to respond to a French "no". The federalists, including Luxembourg, which holds the EU's rotating presidency, want the show of ratifying the treaty to go on. So does Jacques Chirac, who has no desire to achieve pariah status in Europe.
To Mr Blair, pressing ahead smacks of telling the people that they are wrong. If the French sought changes to the treaty to try to win a second referendum, how could Britain and others meanwhile ask their people to vote on the existing treaty?
When Mr Blair shelves the British referendum, as I expect him to if the French say "no", he will be accused of a betrayal by our Eurosceptic-dominated newspapers. But it would be wrong to see his pledge as a cynical manoeuvre he had no intention of keeping.
On the face of it, Mr Blair might be relieved to shelve a difficult-to-win referendum that could all too easily have become a vote on whether he should leave Downing Street immediately. The truth is more complex. In many ways, he would relish the much-postponed crusade on Europe he discussed with Lord Jenkins 10 years ago.
His advisers believe the battle for the constitution, which could be presented as preserving the status quo, would be easier to win than the ever-receding referendum on the euro, a leap in the dark.
Not that a French "no" would mean a quiet life for Mr Blair. Far from it. Britain takes over the EU presidency in July and so would have to sweep up the mess. An operation to salvage some parts of the treaty would be launched. The problem is that different EU countries would want to rescue different bits of it.
There could well be a debate on two futures for Europe, with Mr Blair leading the charge for an Anglo-Saxon, economically-flexible EU - which would have been rejected by many French voters - while President Chirac trumpets a social Europe.
Mr Blair would try to use such a debate for domestic purposes too, trying to win public support for Labour's "pro-Europe, pro-reform" stance - an apparently contradictory message he has never fully explained.
But without the focus of a referendum, it is difficult to see the Europe debate catching fire. It would be another case of paradise postponed - this time, almost certainly until after Mr Blair's departure. As he casts around for a legacy, Mr Blair is running out of options.Reuse content