In the resistance underground, his final nom de guerre was Chaban; after World War II, he formally changed his name to Chaban-Delmas.

A member of the Radical Party, he finally joined the Gaullist Rally of the French People (RPF), which opposed the Fourth Republic's governments.

He "tied up" with centre-left parties and joined Pierre Mendès-France's cabinet one year later as Minister of Public Works.

He took part in the foundation of the Union for the New Republic (UNR) and was elected, against de Gaulle's will, chairman of the National Assembly.

Unlike some Gaullists, for instance, Jacques Soustelle, he supported de Gaulle's policy to end the Algerian War of Independence.

During the 1959 UNR Congress, he was the first politician to evoke a "reserved presidential domain," composed chiefly of defence and diplomacy.

In 1969, when Georges Pompidou acceded to the presidency, he chose Chaban-Delmas, who had concluded that the May 68 crisis was the consequence of a strained and conflicted society, as prime minister.

Indeed, his advisers who inspired the "new society" programme were considered as close to the centre-left (Simon Nora and Jacques Delors who would serve as Finance Minister under François Mitterrand).

The satirical paper Le Canard Enchaîné accused him of breaking the law through tax evasion and in 1972, Chaban-Delmas canvassed for a vote of confidence in the Assembly.

He was supported by the "lords of gaullism", but 43 personalities close to the late president, led by Jacques Chirac, published the Call of the 43 in favour of the candidacy of Valéry Giscard d'Estaing.

Chaban-Delmas stood in the Gaullist Party (RPR) and, in spite of Chirac's leadership, returned to the chair of the National Assembly (1978–1981).