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Could Marine Le Pen beat the odds and win the French election?

Marine Le Pen, the embodiment of far-right populist discontent in France who has drawn comparisons to Donald Trump, is trailing her opponent in national opinion polls ahead of Sunday's presidential election by a significant margin.

John Heilemann: Trump victory proves polling is broken

But as Brexit proved in Britain and the election of Donald Trump reinforced in the U.S., opinion polls get it wrong sometimes, and a very different of measure of support suggests Le Pen could give her centrist opponent Emmanuel Macron a real run for his money this weekend.

Hours before the rivals faced off in a heated, personality-bashing TV debate on Wednesday evening, a social media company released data suggesting the diametrically opposed candidates enjoy near-equal support.

SocialFlow co-founder Frank Speiser says data on mentions of both candidates on Facebook and other social media platforms in the week leading up to the election suggest they are running in a "virtual dead heat," and thus, "any attempts to call an early victor in the election now would be absolute conjecture." 

While SocialFlow's data do not discern between positive and negative mentions on Facebook, Speiser says the company used similar methodology to accurately predict Britain's vote to break away from the European Union (Brexit), "to the exact percentage," and Mr. Trump's landslide win in November -- both of which took most traditional pollsters by surprise.

Speiser tells CBS News that SocialFlow's data seem to reveal voter intent that traditional polling effectively misses. It does that, he says, by guaging the attitudes of people "who tend not to engage in the political process." In other words, first time voters and others who are "not the type of people who would ever respond to a poll."

Two candidates move to second round in French election

Nevertheless, the most recent polling in France gives Macron an advantage of about 20 points heading into the vote, and his performance in the fiery Wednesday night debate -- the only live televised debate to take place before the election -- appeared to bolster his standing.

A snap poll conducted immediately after the debate for France's BFMTV network showed 63 percent of viewers believed Macron had bettered his rival.

Le Pen has long-dismissed polls suggesting she cannot win the election, pointing out to Anderson Cooper in an interview for "60 Minutes" earlier this year that they "also said that Brexit wasn't going to happen, and that Donald Trump wasn't going to be elected -- wasn't even going to be his party's nominee. Well, they're saying that less and less now." 

Speiser, of SocialFlow, said data on social media interactions both during and after the debate followed the trend of the pre-debate data, showing near equal engagement with Macron and Le Pen content. 

The Wednesday night debate turned into an uncivil, no-holds-barred head-on clash of styles, politics and personalities.

Macron called his far-right opponent a "parasite" who would lead the country into civil war. She painted the former banker as a lackey of big business who is soft on Islamic extremism.

Candidates for the 2017 presidential election, Emmanuel Macron (R), head of the political movement En Marche!, or Onwards!, and Marine Le Pen, of the French National Front (FN) party, pose prior to the start of a live prime-time debate in the studios of French television station France 2, and French private station TF1 in La Plaine-Saint-Denis, near Paris, France, May 3, 2017. REUTERS

Neither landed a knockout blow in the 2½-hour prime-time slugfest -- but not for lack of trying. The tone was ill-tempered from the get-go, with no common ground or love lost between the two candidates and their polar opposite plans and visions for France. Both sought to destabilize each other and neither really succeeded.

For the large cohort of voters who remain undecided, the debate at least had the merit of making abundantly clear the stark choice facing them at the ballot box Sunday.

Neither candidate announced major shifts in their policy platforms. They instead spent much of their carefully monitored allotments of time attacking each other -- often personally.

Le Pen

Le Pen's choicest barb came as she argued that Macron, if elected, would be in the pocket of German Chancellor Angela Merkel. "Either way France will be led by a woman; either me or Madame Merkel," she said derisively.

Macron gave as good as he got and, at times, got the upper hand with his pithy slights. In the closing minutes, he used a sharp-tongued monologue to target one of Le Pen's biggest vulnerabilities: her father, Jean-Marie Le Pen, the extreme-right former presidential candidate repeatedly convicted for hate speech and who founded her party, the National Front.

Throughout, Macron portrayed Marine Le Pen as an empty shell, shaky on details and facts, seeking to profit politically by stirring up hatred and the anger of French voters -- a dominant theme of the campaign -- without feasible proposals. He called her "the high priestess of fear."

"Your project consists of telling the French people, 'This person is horrible.' It's to cast dirt. It's to lead a campaign of lies and falsifications. Your project lives off fear and lies. That's what sustains you. That's what sustained your father for decades. That's what nourished the extreme right and that is what created you," Macron said. "You are its parasite."

"What class!" Le Pen retorted.

One of the most heated exchanges was on terrorism -- a top concern for Le Pen's voters and many French in the wake of repeated attacks since 2015. Saying that Islamic extremists must be "eradicated," Le Pen said Macron wouldn't be up to the task.

"You won't do that," she charged.

Saying France's fight against terror would be his priority if elected, Macron countered that Le Pen's anti-terror plans would play into extremists' hands and divide France.

"The trap they're setting for us, the one that you're proposing, is civil war. What the terrorists expect is division among ourselves. What the terrorists expect is heinous speech," Macron said.

They clashed over France's finances, its future and their respective proposals for tackling its ills. He scoffed at her monetary plans, saying reintroducing a franc for purchases within France but allowing big firms to continue using the shared euro currency that Le Pen wants to abandon made no sense.

She dismissed his economic proposals with sweeping critiques and bristled at his suggestions that she didn't understand how finance and business work.

"You're trying to play with me like a professor with a pupil," she said.

They also clashed over foreign policy. Macron said he wants to work with U.S. President Donald Trump on intelligence-sharing, at the United Nations and on climate change. He spoke less favorably of Russian President Vladimir Putin, saying on many subjects "we don't have the same values and priorities."

"We have no reason to be in a cold war with Russia," Le Pen said.

He said that her election would harm France's image abroad, charging: "The world won't look favorably on us."

Trailing in polls, Le Pen needed but failed to land a knockout blow in the debate to erode the seemingly comfortable lead of Macron.

For Macron, the priority was to prevent Le Pen from making up ground in the race's final days, and it appears he accomplished that mission -- unless the polls are proven wrong, yet again.

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