A member of The Republicans, he was elected to the National Assembly for the third constituency of Drôme from 1993 to 1997 and again from 2002 until 2017, with a brief interruption in 2007, when he was appointed Minister of the Overseas by President Jacques Chirac in the last weeks of his second term, replacing François Baroin, who became Minister of the Interior.

He was national secretary in the Republican Party that was dissolved in 1997 and later in Liberal Democracy, established the same year.

In 1998, he was a candidate for president of the Union for French Democracy, receiving 10% of the vote against François Bayrou.

[1] From 1995 to 1997 and again from 2002 until 2017, Mariton served on the Committee on Finance, Economic Affairs and Budgetary Control.

Although being part of The Reformers, a liberal faction within the party, he opposed the passage of Law 2013-404, which legalised same-sex marriage in France.