The killing of a policeman by a suspected Islamist militant pushed national security to the top of the French political agenda on Friday, two days before the presidential election. One policeman was shot dead and two others were wounded in Thursday night's attack.
With the first round of voting in the two-stage election taking place on Sunday, far-right nationalist candidate Marine Le Pen promised tougher immigration and border controls to beat "Islamist terrorism" if elected.
Centrist Emmanuel Macron, who narrowly leads a tight race ahead of Le Pen, said the solutions were not as simple as she suggested, and that there was "no such thing as zero risk".
There are four leading candidates in a race that is still too close to call. Sunday's voting will be followed by a runoff on 7 May between the top two candidates. The first poll conducted entirely after Thursday's attack suggested Le Pen had gained some ground on Macron.
Attack in Heart of Paris Turns Elections Unpredictable
The attack on the Champs-Elysees boulevard in the very heart of the capital added a new source of unpredictability to an election that will decide the management of France's 2.2 trillion euro economy, which vies with Britain for the rank of fifth largest in the world.
The outcome could also have a bearing on France's place in the world and in a European Union still reeling from Britain's decision to leave. While Macron is ardently pro-EU, Le Pen wants to quit its single currency and potentially hold a referendum on leaving the bloc.
All the candidates are seeking to woo the huge number of undecideds - some 31 percent of those likely to vote, according to an Ipsos poll on Friday.
Fillon also seized on the attack, which was claimed by the militant group Islamic State, saying the fight against "Islamist totalitarianism" should be the priority of the next president. "It's us or them," he said.
Elite Security Units Mobilized for Upcoming Elections
After an emergency meeting of security officials, Prime Minister Bernard Cazeneuve said security forces, including elite units, were on alert to back up the 50,000 police earmarked to ensure safety during the election.
The government is fully mobilised. Nothing must be allowed to impede the fundamental democratic process of our country. It falls to us not to give in to fear and intimidation and manipulation, which would play into the hands of the enemy.
Controls on immigration and national security are cornerstones of Le Pen's National Front agenda, and on Friday she said she would reinstate border checks and expel foreigners who are on intelligence services' watch lists.
Macron was quick to respond. He said:
I’ve heard Madame Le Pen saying again recently that, with her in charge, certain attacks would have been avoided. There’s no such thing as zero risk. Anyone who pretends (otherwise) is both irresponsible and deceitful.
Macron and Le Pen Leading
In an Elabe poll conducted on Wednesday and Thursday, and published on Friday, both Fillon and Melenchon were seen narrowing Macron and Le Pen's lead.
Should both Macron and Le Pen make it to the second round, he was likely to win the runoff by 65 percent to 35, according to the survey for BFM TV and L'Express magazine.
Fillon, who has slowly clawed back some ground lost after a fake jobs scandal, saw his score in the first round rise half a percentage point to 20 percent.
Melenchon, who would hike taxes on the rich and spend 100 billion euros ($107 billion) of borrowed money on vast housebuilding and renewable energy projects, gained 1.5 points to 19.5 percent as he built further on the momentum he has generated with strong performances in television debates.
If Melenchon makes it to the runoff, he was projected by the survey to beat either Le Pen or Fillon by comfortable margins, although he was seen losing to Macron by 41 percent to 59.