[4] His parents immigrated to Canada and settled in Montreal in 1958,[5] but relocated later in the year to Loretteville, near Quebec City.

Deltell ran as the Action démocratique du Québec candidate in the district of Chauveau in the 2008 provincial election.

[citation needed] He ceased being leader of the ADQ upon the dissolution of the party into the new movement established by François Legault, the Coalition Avenir Québec.

Following much speculation, Deltell announced on April 7, 2015, that he would be running for the Conservative Party of Canada in the riding of Louis-Saint-Laurent in the upcoming federal election.

Opposition leader Rona Ambrose named Deltell the party's Quebec lieutenant and critic for Employment, Workforce and Labour,[11] and he has been noted for his strong performances during Question Period.

[10] Despite being a newcomer to federal politics, Deltell was mentioned as a possible leadership candidate to replace former leader Stephen Harper.

On October 16, 2016, Deltell was appointed Official Opposition Finance Critic by Rona Ambrose, interim leader of the Conservative Party of Canada.

[14] Conservative Leader Andrew Scheer announced his shadow cabinet on August 30, 2017, and named Deltell as critic for the Treasury Board.