[3] Saint-Martin represented the 3rd constituency of the Val-de-Marne department in the National Assembly from 2017 to 2022 as a member of La République En Marche!

[7] In late 2018, Saint-Martin was offered to join the government of Prime Minister Édouard Philippe but declined a post as Secretary of State at the Ministry of the Economy and Finance under the leadership of Bruno Le Maire.

[8] In June 2019, Philippe entrusted him with a mission to reform the national system for the identification, seizure and confiscation of criminal assets.

[9] From 2020, Saint-Martin served as the Parliament's lead rapporteur on the annual budget of France; he succeeded Joël Giraud.

[13] In the 2022 legislative election, Saint-Martin ran for reelection to the National Assembly but lost his seat to Louis Boyard of La France Insoumise.