Fewer than half of French voters went to the polls, indicating a wide indifference about the importance of the regional vote and undermining the claim by the opposition of a wave of anger at Mr. Sarkozy.

What struck French analysts was the good performance of a coalition of green parties, known as Europe Ecology, led by Daniel Cohn-Bendit, and the revival of the far-right, anti-immigrant National Front, which was running almost even with the ecologists for third place.

Mr. Sarkozy failed to take many votes from the National Front, which had been part of his strategy and was why, some analysts suggested, he had kicked off a national “debate” on the French identity and had begun moves to ban the full facial veil of Muslim women in France.

Results released by the Interior Ministry with about 80 percent of the votes counted showed the Socialists and their allies, who already control 20 of the 22 regions of mainland France, winning about 29 percent of the vote. Mr. Sarkozy’s Union for a Popular Movement had 26 percent to 27 percent. Europe Ecology had 11.6 percent, while the National Front had 11.7 percent. The so-called third party of the Democratic Movement was trailing badly with 4.3 percent of the vote, behind a far-left party.

Whether the Socialists will succeed in their aim to win a clean sweep of the mainland’s regions will not be known until after a second and final ballot next Sunday, when parties that obtained at least 10 percent in the first round will face off individually or in coalitions.