He started administrative assistant work when he was sixteen and then, after his military service,[3] he entered politics at age 26, joining the POF of Jules Guesde.

He preferred creating autonomous socialist groups; and was an advocate of freethought, freemasonry, and the International League for Human Rights.

Accused of political guilt, in 1907, the new mayor of Romans-sur-Isère, Dr. Ernest Gailly, dismissed Nadi, through the influence of Joseph Caillaux.

Chaired by Nadi, the first Congress was held in La Roche-sur-Yon, from which emerged the Socialist Federation of Vendee, with a hundred members.

[4] In this role, he established a municipal socialism, with specific attention to the construction of housing for workers, redeveloping former barracks that were old religious buildings.

At SFIO's 1920 Tours Congress, he decided to join the PCF, but was expelled two years later, along with E. Soutif,[9] as Nadi was repelled by Bolshevism and its requirement to denounce Freemasonry.