During his studies, he completed a year abroad at Johns Hopkins University and an internship in the office of Carolyn McCarthy at the United States House of Representatives in Washington, D.C.[3] Dumont served as Mayor of Marck from 2014 to 2017.

[7] Dumont endorsed Christian Jacob as the party’s chairman in the run-up to the Republicans’ 2019 convention,[8] and later supported Aurélien Pradié’s candidacy to succeed Jacob in 2022; in the second round of voting, he eventually supported Éric Ciotti.

In the 2024 election, he lost his seat in the second round to National Rally's Marc de Fleurian.

[10] In the summer of 2020, Dumont disputed the claims of Priti Patel, the British Home Secretary that French authorities were not stopping migrants from leaving France and crossing the English Channel.

[14] After the November 2021 English Channel disaster, Dumont spoke to CNN and criticized Prime Minister Boris Johnson.