Mr Delors, 69, who topped the opinion polls for a month, said on Sunday that he had finally decided against being the Socialist Party candidate to succeed Francois Mitterrand, whose second seven-year term ends in May.
The news sent shock-waves through the French left, which had seen Mr Delors' candidature as a way to regain the upper hand after the Socialists were trounced in parliamentary elections last year. Mr Delors' decision, on personal and political grounds, virtually handed the presidency to the right.
Almost immediately, there was speculation that Bernard Tapie, the controversial businessman-turned-politician, would stand for his centre-left Radical Party, a move which would weaken the left's chances even further by dividing its support. The Socialists will choose a candidate next month.
So far, two mainstream conservative candidates are in the race - Jacques Chirac and Edouard Balladur, the Gaullist Prime Minister. In the short term, Mr Chirac, also a Gaullist, seems most likely to benefit. So far, only Mr Chirac has officially announced his candidature.
Now Mr Chirac can tackle Mr Balladur head-on without damaging the right's chances. Given that Mr Chirac, the Mayor of Paris and twice a former prime minister, is more used to the rough-and-tumble of political campaigning, he can be expected to use all his resources to fight the less experienced Mr Balladur.
Only one politician of any stature could try and exploit the centrist vote and take on Mr Chirac on his own terms - Raymond Barre, 70, who was prime minister for five years from 1976 under President Valery Giscard d'Estaing and stood in the last presidential election in 1988. Then, Mr Barre was eliminated in the first round, although opinion pollsters had for a while predicted that he could beat Mr Mitterrand. In the event, Mr Mitterrand beat Mr Chirac in the second round.
In a newspaper interview three months ago, Mr Mitterrand said that he believed Mr Delors and Mr Barre would be the most fitting successors.
Only the two top candidates from the first vote on 23 April will go forward to the second round on 7 May. Mr Barre, facing either Mr Chirac or Mr Balladur, would probably take not just the centre's votes but also most of the left's.
Mr Delors, aside from indicating his preference to retire from active public life once he leaves the European Commission next month, said one of the problems for him as president would have been to find partners who would govern with him.
In the media and among politicians, the overwhelming reaction to Mr Delors' decision was one of respect for a man who, faced with the probability of his country's top office, had decided the disadvantages were too great. The daily Liberation said he had the qualities to be president, "especially the rarest of them all: intellectual honesty".
Other analysts suggested France could expect a bout of "politicians' politics", with little thought for real issues. Le Monde said France's social problems cried out for a decent campaign.
Jean-Marie Colombani, the editor, wrote: "Personal rivalries should not be allowed to obscure the exchange of ideas which France was expecting and which was beginning to develop."Reuse content