Paris (CNN) It has been one of the most unpredictable and dramatic presidential campaigns in French political history -- and with less than a week to go before the election, the outcome remains too close to call.

Only a few weeks ago, it appeared almost guaranteed that the French electorate would vote for a face off between National Front Leader Marine Le Pen and independent candidate Emmanuel Macron.

But as Sunday's first round of voting draws ever closer, the political whirlwind that is far-left candidate Jean-Luc Mélenchon appears to be gathering speed.

Will Le Pen ease through? Can Macron persuade voters he's got a plan? Or will the left-wing firebrand Mélenchon cause widespread shock?

Marine Le Pen

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Le Pen is intensifying her anti-immigration rhetoric, telling a crowd at the Zenith arena Monday night that her first move as president would be to impose a temporary ban on legal immigration to France.

"I will set up a moratorium on all legal immigration to stop this delirium, this uncontrolled situation," she said.

The National Front leader gave a similar message to supporters Sunday, telling the crowd of about 5,000 people she would "reinstate France's borders."

When she mentioned the European Union, the crowd booed, and she repeated her vow to take France out of the bloc, as well as from the border-free Schengen area.

"Mass immigration is not an opportunity for France, it's a tragedy for France," she told supporters.

"The French sometimes have fewer rights than foreigners -- even illegal ones," she added.

On a night of tension, security personnel were forced to wrestle a protester to the ground after she ran toward Le Pen on the stage.

Outside the venue in northeast Paris Monday night, anti-National Front protesters clashed with police, according to CNN partner BFM-TV.

Emmanuel Macron

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Le Pen's closest rival, independent centrist Emmanuel Macron, would become the youngest man to lead France since Napoleon if he wins.

The 39-year-old addressed supporters at the Bercy arena in Paris, accusing his opponents of wanting to take the country back to the past.

While his rivals have been embroiled in scandal throughout the campaign, the youthful Macron has so far managed to sidestep the controversy.

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But his place in the second round of voting is under threat from far-left firebrand Jean-Luc Mélenchon.

There remains a deep skepticism within the French electorate of the establishment, and Macron -- a former economy minister and investment banker -- could be affected by that affiliation.

Macron's lack of experience, lack of party and tender years could go against him.

"I want to take the best of the left wing, of the right wing, and even the best of the center," Macron told supporters.

"Some would like France to become Cuba without the sun or Venezuela without the oil," he said of Mélenchon, referring to the left-wing candidate's mantra.

Jean-Luc Mélenchon

Mélenchon could yet be the wildcard in an election that has seen twists and turns at every opportunity.

Support for the 65-year-old has surged in recent weeks, following his impressive performances in the presidential television debates.

A charismatic speaker who is popular with younger voters, his easy conversational style has won over supporters.

He's the left's best shot at beating the far-right in the second round -- and he also offers something the French electorate is craving: change.

But that same offering may be his undoing, with his policies unlikely to appeal to all voters.

Mélenchon advocates withdrawing from NATO and the International Monetary Fund. He also wants to renegotiate EU rules, and calls for a referendum on whether France should leave bloc if the rules are not changed.

Raising the minimum wage and strictly limiting the work week to 35 hours are other goals of his campaign.

François Fillon

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Republican candidate Fillon is still hanging in there, despite a campaign thrown off track by scandal.

Fillon, 63, is under investigation on multiple counts, including embezzlement of public funds.

His problems started when French newspaper Le Canard Enchainé reported that his wife and two of his adult children earned nearly €1 million ($1.08 million) as parliamentary assistants, but allegedly never performed any work in the jobs.

The candidate has rejected the claims, saying his wife Penelope, who has also been charged, worked for 15 years as his deputy and handled several roles, including managing his schedule and representing him at cultural events. He also said his daughter and son were employed in similar positions for 15 months and six months respectively, which he said is not illegal, but was an "error of judgment."

While the allegations have harmed his campaign, he remains in the race, albeit with only an outside chance of a top-two finish.