The party's power declined after the Dien Bien Phu military disaster in Indochina in 1954, and it remained in opposition for most of the last two years of the Fourth Republic after the 1956 elections.

On October 5, 1962, 107 CNIP deputies voted no-confidence in Georges Pompidou's government,[5] opposing de Gaulle's constitutional reform on the election of the president by universal suffrage.

However, the CNIP cabinet ministers, led by future president Valéry Giscard d'Estaing, continued to support de Gaulle.

Severely weakened by the split and its opposition to the October 1962 referendum, it suffered a major defeat in the 1962, left with only a handful of seats.

It allied itself with the Popular Republican Movement (MRP) to form the Democratic Centre, later known as Progress and Modern Democracy, in which the CNIP was only a small component.

[2] In the 1986 election, CNIP members appeared on RPR-UDF lists but it won three seats through local alliances with the FN in some departments.

On September 19, 2012, Bourdouleix - the party's only remaining deputy - announced that the CNIP was joining Borloo's centre-right Union of Democrats and Independents (UDI).

But on 10 September, the CNIP was expelled from the UDI after Gilles Bourdouleix had declared the "Maybe Hitler hadn't killed enough Romas".