[2] His grandfather was Charles Ignace Plichon (1814–88), a company director who was first elected deputy in 1846, and then held office almost continuously until his death.

[5] At the age of 29 Plichon ran for election in the second district of Hazebrouck, Nord, as candidate of the Republican Union.

He defended the family, stood for protection of commerce and industry, and supported higher prices for farmers and the right for them to organize.

He was interested in many rural questions such as duties on imported hops, veterinary medicine, sharecropping and wheat.

He intervened on the subjects of tax relief for mobilized people, maintaining territorial integrity, suppressing espionage and excluding communists from the chamber of deputies.

After the defeat of France, on 10 July 1940 he voted in favor of granting the requested constitutional powers to Marshal Philippe Pétain.