But then came the 1973 oil crisis, economic instability, recession and high unemployment — especially among working class youths who turned to petty crime and caused a rise in delinquency, said Laurent Bonelli, a political scientist and expert on the history of crime at Paris Nanterre University.
Demographically, France had a young population, with the median age at a postwar low of about 31 — the current median age is about 41. In 1976, France also legalized family reunification, marking the start of an influx of immigrants from sub-Saharan and Northern Africa.
Those factors helped turn crime into a hot-button issue in the late 1970s, and it has episodically defined presidential politics since.
“Security became a political issue, with politicians making law and order their trademark,” Mr. Bonelli said.
The National Rally, the far-right party formerly known as the National Front, became a political force in the mid-1980s under Ms. Le Pen’s father, Jean-Marie Le Pen.
In 2002, the Socialist candidate, Lionel Jospin, an early front-runner, failed to qualify for the second round of the presidential election largely because he was regarded as being weak on crime. Instead, Mr. Le Pen reached the runoff phase for the first time, eventually losing in a landslide to the conservative, Jacques Chirac.
But in the following presidential election, of 2007, Mr. Le Pen performed poorly, losing votes to a politician who had fully grasped the importance of crime as an issue: Nicolas Sarkozy. Mr. Sarkozy, as interior minister, had once said that he would clean out an immigrant-heavy banlieue, or suburb, “with a Kärcher’’ — a high-pressure water hose used to wash off graffiti.