He was one of the co-founders of the National Front (FN) in October 1972, becoming a member of its directing committee. But Gaucher then participated in the split in 1974 leading to the creation of the "Parti des forces nouvelles" (PFN), gathering radical activists who considered Jean-Marie Le Pen to be too "moderate." There, he contributed to the magazine "Initiative nationale". Gaucher was a member of the central committee of the PFN in 1974, and then of the political bureau in 1976. He was the PFN's representative during the Eurodroite meeting in Paris on 28 June 1978, which gathered the Italian MSI, the Spanish "Fuerza Nueva" and the Belgian "Forces Nouvelles" along with the PFN for the 1979 European elections. In 1979, he quit the PFN along with François Brigneau to rejoin the FN, at the request of Jean-Pierre Stirbois.