Conservative President Nicolas Sarkozy's party took a drubbing in local elections, seen as a test ahead of next year's presidential vote, and the far-right National Front left its first footprint in France's smallest administrative districts.
The opposition Socialist Party was the big winner in the second round of balloting in the nation's cantons, with nearly 36% of the vote, according to the Interior Ministry, while Mr Sarkozy's UMP party took 20%.
The National Front had 11.7% - and won in at least two cantons, a first. It was competing in only 403 of the races for 1,566 seats.
The turnout was less than 46% - the lowest ever in a vote in cantons, said Interior Minister Claude Gueant. Results were not final.
The French were voting for the local officials whose decisions help govern daily life. A first-round vote was held a week ago.
The results amount to "spectacular progress" for the National Front and a "terrible disavowal for the president," National Front leader Marine Le Pen said on French television.
"I think we can say that the recomposition of French political life is under way," she said.
The National Front results were down from the party's 15% in last week's first round, but suggested that the bid by its new leader - daughter of party founder Jean-Marie Le Pen - to soften the extreme-right message was working.
The party nevertheless failed to win in two key districts that had been considered in its pocket, including in Montigny-en-Gohelle, Marine Le Pen's own area in the Nord-Pas de Calais region. Party secretary general Steeve Briois was defeated.
The unpopular Mr Sarkozy has been attacked by the opposition for cost-cutting measures, including in national education. He is perceived as being too cozy with corporate interests.
He and his party have tried to lure far-right voters by focusing on themes dear to the National Front like immigration and the integration of Muslims in French society. Islam is the second religion in France after Roman Catholicism. He recently visited a pilgrimage site to praise France's "Christian roots".
But those efforts appeared insufficient to counter the left, or draw the far right.
"Today, the French opened the road to change" and showed it is possible to "believe in another France," said Socialist Party leader Martine Aubry.
The leftist wave that the Socialists predicted would sweep the country did not happen. However, the party, which held the majority of the nation's more than 2,000 cantons, made gains.
"We're obviously a bit disappointed," said UMP leader Jean-Francois Cope.
Prime minister Francois Fillon was more to the point.
"The left is progressing, but the slide of the (conservative) majority is less than predicted," he said.
Mr Fillon warned in a statement that the National Front score "shows that the protest vote must not be underestimated or trivialised. This party must be fought and the reasons for its audience lucidly evaluated and treated."