Marine Le Pen's far-right National Front lost election run-offs on Sunday in three key target regions despite topping last week's first round, exit polls showed, making Nicolas Sarkozy's conservatives and their allies the clear winner in all three.
The result followed the withdrawal of President Francois Hollande's Socialist Party in two of the regions for the decisive run-off round, and its call on supporters to vote tactically to keep the FN out of power.
The regional election run-off, in which the conservatives won seven constituencies and the Socialists five, was no real victory for either of these two mainstream parties, shaken by the far-right's growing appeal to disillusioned voters.
Boosted by fears about security and immigration after the Islamist militant attacks in Paris a month ago that killed 130 people, the National Front (FN) had won more votes than any other party nationally in last week's first round.
Aside from immigration concerns, which have been boosting nationalistic parties in other European countries too, the FN's rise has been built on deep disaffection with mainstream politics among French voters and a frustration with Hollande's inability to reduce unemployment.
Although it won no region on Sunday after the Socialists pulled out of its key target regions, the FN still recorded its best showing in its history.
"Tonight, there is no place for relief or triumphalism," Socialist Prime Minister Manuel Valls said. "The danger posed by the far right has not gone away; far from it."
Sarkozy struck a similar theme, calling the strong FN showing a "warning sent to all politicians, ourselves included, in the first round".
"We now have to take the time for in-depth debates about what worries the French, who expect strong and precise answers," he said, citing Europe, unemployment, security and national identity as key issues.
Le Pen, who had hoped to use regional power as a springboard to boost her chances in 2017 presidential elections, lost by a huge margin in northern France on Sunday, where she led her party's ticket, attracting 42.8 percent of the votes in the run-off vs 57.2 percent for the conservatives.
In the south-east, where Le Pen's niece Marion Marechal-Le Pen was the FN's lead candidate, the conservatives scored 54.5 percent and the FN 45.5, the poll said.
"There are victories that shame the winners," Marechal-Le Pen said, slamming the Socialists' decision to pull out of the race for the run-off.
The turnout in both regions was more than 61 percent, up significantly from the first round, the poll showed.
In the eastern region, where the Socialists did not withdraw, the center right won 48.4 percent against the FN's 36.4 percent, according to a separate poll by TNS Sofres-One Point.
Long content with attracting protest votes, the FN has changed strategy since Le Pen took the party over from her father Jean-Marie in 2011, seeking to build a base of locally elected officials to target the top levels of power.
But while it has been winning more and more votes in each election since then, its isolation in France's politics means it cannot strike the alliances it would need to win major constituencies. So it failed once more on Sunday to turn growing popularity into power.