KEY POINTS:
A third presidential defeat in succession is a calamity for the French centre-left.
It is also a stinging, personal rebuff for Segolene Royal.
A savage debate will now rage in the Socialist Party over who was most to blame. Was Royal at fault for fighting "too personal" and too unconventional a campaign and moving too far towards the centre? Or was Royal - as the newspaper Le Monde has suggested - given a losing hand from the start? Royal cannot escape part of the blame. After a brilliant primary campaign, she stumbled and stuttered. She failed to find her true voice as a tough but caring, new kind of Socialist until the final days of the second round.
All the same, yesterday's overwhelming defeat - and the even the more calamitous loss in the first round in 2002 - are not Royal's failure alone. They flow from the failure of the French centre-left, over many years, to adapt to the new realities of global competition and shrinking national and state control.
Royal was a popular but marginal figure on the centre-left until 18 months ago. She was chosen as Socialist candidate last November as the person most capable of beating Nicolas Sarkozy. In defeat, she will find it difficult to remain a leading figure in French centre-left, politics.
She may have to retreat to her fiefdom as President of the Poitou-Charente region - but not willingly.
Her partner, Francois Hollande, is the Socialist leader. Given the extent of last night's defeat, he may now also find it hard to keep his post.
There is a deeper problem for the Socialists. One of the lessons of the first round of this year's presidential election is that the combined left - from Socialists to Trotskyists via Communists and Greens - has shrunk to just over one third of the electorate.
The whole spectrum of French politics has shifted to the right. Within that spectrum, Royal's score in the first round - 25.8 per cent - was historically a high figure for a Socialist. The problem was that the "rest of the left" totalled only about 10 per cent, leaving her scrambling for votes from Francois Bayrou's "sexy centre".
Political historians may come to see Royal as something of a visionary. She tried to reconcile left-wing aims - social justice, equality of opportunity - with conservative family values and a pragmatic "whatever works" approach to government.
She also began the process of replacing the old tradition of Socialist alliances with the hard and dinosaur left with a new opening towards the centre ground. This may have been forced upon her by the desperation of starting the second round 2 million votes behind Sarkozy. Still she recognised the new electoral reality.
This will be the epicentre of the furious debate which will break out in the Socialist Party in the next few days (and had already started last night).
Some Socialist leaders will argue that the party should build bridges with the Trotskyists and surviving Communists.
"Bridges to where?" the social-democrats will ask.
Links with the new centre party planned by Francois Bayrou, will give the Socialists a historic opportunity to shake off the old statist dogma.
The outcome of this debate must await the parliamentary elections which follow on June 10 and 17. Hollande will presumably lead the Socialists into this battle, hoping to keep a Sarkozy parliamentary majority within reasonable bounds.
Bayrou hopes to win a solid bloc of centrist seats for his new Democratic Party, despite repudiating - and virtually spitting on - his old alliance with Sarkozy's centre-right UMP party.
If he brings off his gamble, there will be senior figures on the right of the Socialist Party who will argue for a new formal alliance between left and centre. There is just a possibility that the Socialist Party might split - along the lines of the Labour-SDP split in Britain in the early 1980s.
Sarkozy is no Margaret Thatcher but - like her - he may be inadvertently responsible in the next few years for the belated modernisation of his political enemies.
- INDEPENDENT