The prospect could be a reality if Le Pen fails to get 500 elected officials to sponsor her candidacy.
Under French law, any presidential candidate needs 500 signatures from elected representatives in at least 30 different departments across the country or in France's overseas territories.
Le Pen told RTL radio on Thursday that she was still 150 short of the target number and risked being excluded from the vote on April 22nd.
A Sunday newspaper, Journal du Dimanche, published an opinion poll at the weekend showing that the fortunes of current president Nicolas Sarkozy improve markedly without Le Pen in the picture.
In that case, Sarkozy and his Socialist rival François Hollande would each get 33 percent of the vote.
Current polls give the president around 24 percent compared to Hollande's 30 percent. Le Pen is just behind on around 20 percent, threatening to overtake the president and secure a place in the final two-way runoff on May 6th.
Le Pen told a meeting in Toulouse on Sunday that the scenario in the poll was "the dream of the political class."
"If I'm not there will you vote for Nicolas Sarkozy, for François Hollande?" she said, as the audience booed and whistled.
"There is your response to their pathetic opinion polls and pathetic manipulations," she said.
Le Pen has been accused of lying about her lack of signatures by politicians on left and right.
"It's a bluff," said finance minister François Baroin on radio station Europe 1. "Her father used to do the same thing," he said in a reference to the former leader of the Front National, Jean-Marie Le Pen.
In fact, Jean-Marie Le Pen failed to get enough signatures on one occasion in 1981, when François Mitterrand was the election victor.