The UDR was the successor to Charles de Gaulle's earlier party, the Rally of the French People, and was organised in 1958, along with the founding of the Fifth Republic as the Union for the New Republic (UNR), and in 1962 merged with the Democratic Union of Labour, a left-wing Gaullist group. In 1967 it was joined by some Christian Democrats to form the Union of Democrats for the Fifth Republic, later dropping the 'Fifth'. After the May 1968 crisis, it formed a right-wing coalition named Union for the Defense of the Republic (UDR); it was subsequently renamed Union of Democrats for the Republic, retaining the abbreviation UDR, in October 1968.
Hibbs, Douglas A., and Nicholas Vasilatos. "Economics and Politics in France: Economic Performance and Mass Political Support for Presidents Pompidou and Giscard d'Estaing." European Journal of Political Research (1981) 9#2 pp: 133-145. online
Wilson, Frank L. "Gaullism without de Gaulle," Western Political Quarterly (1973) 26#3 pp. 485–506 in JSTOR