The weekend vote was to choose a successor to Christophe Castaner, recently appointed interior minister.
Stanislas Guerini is 36-years-old, an MP from Paris, and is said to be close to the head of state. He was elected with 82 percent of votes, easily beating the 18 percent support for his solitary adversary, Joachim Son-Forget.
Guerini’s first task will be to remobilize the electorate with a view to European elections due in May.
French municipal polls will be held in early 2020.
The national council of the ruling party was forced to move the election meeting from central Paris to the suburb of Nogent-sur-Marne because of disruption caused by yellow vest protestors.