Strong supporter and advocate of
revolutionary ideas, he became one of the founder members of the
Société des amis de la Constitution (Jacobins) (11 November 1789), elected
justice of the peace in Lille in 1790, then elected North member of parliament (MP) to
Legislative Assembly in September 1791 where he sat on the
left. On 17 November 1791, he gained attention in Assembly by giving a violent speech against
non-juring priests. He wanted the confinement of War Ministry
Narbonne-Lara but was disapproved by other MP. Throughout that period, Duhem carried out active propaganda for republican ideas in the streets, the Assembly and the
sections. He played a role in the
insurrection of 10 August and, during the night of 10–11 August, he presented the decrees suspending the King and calling for a
National Convention. On 20 August 1792, he required to publish a decree concerning
General Dillon who "lost the confidence of the nation". On 21 August, he was elected secretary of the National Assembly, then sent on a mission to the
Army of the North where he reported that
Maubeuge was threatened by foreign armies. ==The National Convention member==