Ranking third in the polls, her candidacy could split the conservative vote upon which incumbent Nicolas Sarkozy may again have to draw to win the April-May election.
He has overtaken his Socialist challenger François Hollande for the first time in recent polls after launching an attack on the European Union’s trade and immigration policies, suggesting an increased sensitivity to right-wing issues.
Candidates have until Friday to obtain the backing of 500 elected officials to compete in the 22 April first round, after which the two front-runners face off in a 6 May showdown.
Ms Le Pen enjoys around 16 per cent in the polls, but she had complained the reluctance of elected officials to back her publicly had proved an impediment
In a boost to Mr Sarkozy, an Ifop/Fiducial survey yesterday put his first-round score at 28.5 per cent, up from 27 per cent last month and overtaking Mr Hollande, who slipped to 27 per cent from 28.5 per cent previously. The poll gave Mr Hollande 54.5 per cent of the second-round vote to Mr Sarkozy’s 45.5 per cent, a narrower lead as Mr Hollande lost two points and Mr Sarkozy gained two.
“I hope the swallow we saw this morning will make the spring,” Alain Minc, an adviser to Mr Sarkozy, said.
The election is a duel between Mr Sarkozy, who promises tighter immigration controls, structural reforms and policy referendums, and Mr Hollande, who is running on a tax-and-spend programme while also promising to cut the budget deficit.
The poll was taken after Mr Sarkozy told his biggest rally yet on Sunday that he would erect unilateral barriers to trade and immigration unless the European Union toughens it stance.
He also said Europe should have a law, modelled on the Buy American Act, requiring governments to purchase European-made products. He also threatened to pull France out of Europe’s Schengen open-borders zone unless progress was made on controlling immigration.
Mr Hollande said Mr Sarkozy’s move was a sign he was running out of inspiration. “He will try anything,” he told TV news.
Mr Sarkozy is hampered by the fact he is one of France’s least popular presidents, with many frustrated at economic gloom and tired of his flashy style. An Opinionway survey on Monday put his approval rating down one point at 31 per cent, although his disapproval rating dropped two points to 62 per cent.
Half of respondents thought Mr Hollande was running a stronger campaign. Only 27 per cent thought Mr Sarkozy’s campaign was better.
Ms Le Pen, announcing she now has the backing to run, said: “I have my 500 signatures and therefore I will be a candidate in the presidential election.”
A charismatic speaker who has won a strong following since taking over the National Front leadership from her father Jean-Marie Le Pen in January 2011, she no longer seems to have enough support to prevent Mr Hollande and Mr Sarkozy facing each other in the run-off.
Earlier polls had shown her snapping at Mr Sarkozy’s heels, reviving memories of the 2002 election when her father knocked out Socialist Lionel Jospin to reach the run-off against Jacques Chirac, the eventual winner. As in 2007, Mr Sarkozy is leaning to the right to woo National Front support..