The tragic killing of four people outside a Jewish school in Toulouse on Monday by Mohamed Merah, a gunman of Algerian origin, who may also have murdered three Muslim soldiers elsewhere in southern France, and who has ties to Afghanistan, has become a powder keg pivot point in the French presidential election.

With so much of a focus on immigration by both incumbent Nicolas Sarkozy and Front national candidate Marine Le Pen — the campaign just a couple of weeks ago went a round on the threat of halal meat in France — it is not difficult to see how this story could galvanize the campaign in the days ahead in a way that could challenge the calmer, more pro-immigration voices of frontrunner François Hollande of the Parti socialiste.

The shocking event provides both Hollande and Sarkozy a crisis of the first order to demonstrate their particular styles of presidential leadership.

For now, a quick rundown of the responses so far:

Sarkozy suspended his campaign and sounded a note of calm and national unity, holding back on some of the more fiery rhetoric he’s used previously in the campaign to attack current immigration policy:

“Terrorism will not succeed in fracturing our national community,” he said in a TV address as police in Toulouse tried to negotiate the surrender of a self-declared Islamist militant holed up in a flat after a series of killings.

“I say to the entire nation that we must be united,” Sarkozy said after meeting with Muslim and Jewish leaders in the Elysee palace to discuss community relations in the wake of the deadly gun attacks.

The president said that the French should not be tempted by revenge and should understand that the attacks had nothing to do with religion.

Le Pen, predictably, has gone on the attack, even as she has also suspended her campaign:

Miss Le Pen of the National Front – who has previously likened Muslims praying   in the streets to the Nazi occupation of France – claimed the “Islamic   fundamentalist threat has been underestimated in our country and   political-religious groups are developing due to a certain laxism”.

Hollande’s approach mirrored that of the French president’s, as he also suspended his campaign to visit Toulouse, but he sounded a very gentle note of criticism at the tone that politicians, including Sarkozy, have used in the past:

“There are words that influence, that penetrate, that liberate [prejudice]. Those who have positions of   responsibility must control their vocabulary,” [Hollande said.]

Sarkozy’s campaign and UMP allies, however, were quick to charge both Hollande and Le Pen with trying to take advantage of the incident.

Front de Gauche candidate Jean-Luc Mélenchon has not suspended his campaign, but minced no words for his disgust with Le Pen and the anti-immigration rhetoric of the right:

“Continuing the campaign is an act of moral, intellectual and emotional resistance,” said the firebrand leader of the Left Front…. “We must not allow our vigorous democracy to be put on hold by an odious and degenerate murderer.”

His campaign labelled Le Pen and the Front national “vultures” for trying to take political advantage of the tragedy.

François Bayrou has, likewise, not suspended his campaign, but also pointed his finger at French xenophobia and the kind of stigmatization that he said he believes has crept into French society:

Bayrou, of the centrist MoDem party, on Monday said that anti-foreigner sentiment had crept into the election debate and that certain parties “were pointing the finger at people because of their origins and fanning passions in order to gain political capital.”