PARIS — With the candidate of the National Front, Marine Le Pen, calling for a “war on these fundamentalist political religious groups who are killing our children,” it was easy for President Nicolas Sarkozy to take the high road in the sharp political reaction to the terrorist acts of Mohammed Merah, who was killed by the police on Thursday in Toulouse after himself claiming responsibility for killing seven people.

Despite the failure of the French state to catch Mr. Merah before his rampage or to capture him alive, the killings have nonetheless altered the tone of the presidential campaign, which was briefly suspended, tilting it — at least for a little while — in Mr. Sarkozy’s favor.

Despite having built a reputation for toughness on crime and for polarizing comments about immigrants and Islam, Mr. Sarkozy quickly donned the calming, sober cloak of leadership, incarnating France, casting himself as the president who unites and protects, rather than the candidate who divides.

As the issues of this long presidential campaign shift from economic anxiety and joblessness to terrorism and crime, Mr. Sarkozy’s candidacy continues to reap the benefits, political experts say. It is only on issues related to security that he outpolls his main challenger, the Socialist candidate, François Hollande, whose focus has been on the economy.