By Ingrid Melander
PARIS (Reuters) - France's far-right National Front is set to score huge gains in regional elections on Sunday, redrawing the political landscape of the euro zone's second-biggest economy as it gears up for the next presidential election in 2017.
The anti-immigration, anti-Europe party, boosted by fears over the refugee crisis and the Nov. 13 Islamic State attacks that killed 130 in Paris, is seen leading in the first round on Dec. 6 in six out of 13 regions, a survey by Ipsos pollsters showed on Thursday.
The party, known by its initials FN, has become increasingly popular since Marine Le Pen took over the leadership from her father in 2011. It does not govern any region now, but a series of opinion polls shows it is very likely to win one, maybe more, in a run-off on Dec.13.
"Everything is adding up for the National Front to make an unprecedented score," Ifop pollsters analyst Jerome Fourquet said, citing Europe's migrant crisis, the carnage in Paris, and the January attacks in which Islamist militants killed 17 at satirical magazine Charlie Hebdo and a Jewish shop.
"What was once a ceiling for FN votes has become a floor after Charlie, and the FN building is getting taller and taller now thanks to the migrant crisis and the terrorist attacks."
Le Pen herself is seen winning in northern France and her niece Marion Marechal-Le Pen has a good chance of taking over the southeastern region.
Winning the northern Nord-Pas-de-Calais-Picardie region, which with a population of 6 million is France's third biggest, and larger than several European Union countries, would be a very useful stepping stone for the FN as it sets out to convince voters it has the experience to rule the country.
"We're advancing step by step, we're building credibility... this is reassuring French citizens and breaks the 'fear argument' that people use against us," Marechal-Le Pen told Reuters in a recent interview.
Making big gains in the regional ballots would demonstrate that French politics is now a three-way race, after decades of domination by the Socialists and conservatives.
And while FN regional victories would be unlikely to change Socialist President Francois Hollande's policies, they would mean that the question of how to deal with the far-right party and lure its voters back would dominate politics for the next two years.
"It would be a formidable leverage for Marine Le Pen for 2017," pollster Frederic Dabi said.
"FORWARD TO VICTORY"
The prospect is worrying a number of top business leaders and media, which have taken the unusual step of urging voters not to back the FN.
It is a huge headache too for the Socialists and for the opposition conservative Republicans, led by former president Nicolas Sarkozy.
Any party that attracts at least 10 percent of the vote on Sunday will qualify for the run-offs a week later. Opinion polls show the FN, the Republicans and the Socialists are all likely to make the run-off in most regions.
If the three parties all contest the second round, the FN is seen winning in the north and southeast and possibly two or three more regions. But they would fare less well if the Socialists decided to pull out of some run-offs.
This means Hollande's party, who now govern most regions as well as the country, will be put very much on the spot on Sunday night, when an emergency party meeting will decide what to do.
Prime Minister Manuel Valls has said "everything must be done" to keep the FN out of power, including alliances with the conservatives.
But while this has long been a tradition in France, Sarkozy has rejected it outright, as he has for the past four years. And even within the Socialist party, the strategy is proving divisive.
Sarkozy, who lost his bid for a second presidential term when Hollande defeated him in the 2012 election, is hoping that winning the regional vote will set him up to return to the Elysee Palace in 2017. But the FN's growing strength could take the shine off his party's expected victory.
A boost in Hollande's popularity since last month's attacks will make little difference to the election, analysts said, though it might marginally boost turnout among left-wing voters.
While the Socialists' best hope is to limit their losses, a warmly smiling Le Pen concluded a campaign rally in the northern France city of Lille on Monday by telling supporters: "The reconquest starts here ... Forward to victory!"
(Additional reporting by Elizabeth Pineau, Sophie Louet, Emile Picy, Pauline Mevel and Emmanuel Jarry; Editing by Mark Trevelyan)