Henceforth, the UDSR associated itself with the Radical Party, who had been in government during most of the Third Republic, in the Rally of the Republican Lefts (Rassemblement des gauches républicaines or RGR), which presented itself as an alternative to the tripartisme alliance between the SFIO, the MRP and the French Communist Party (PCF).
The UDSR now aligns itself with the Radical Party, who were previously in power during most of the Third Republic. The Radical Party is part of a political movement called the Rally of the Republican Lefts (Rassemblement des gauches républicaines or RGR), which opposes the existing tripartisme alliance between the SFIO, the MRP and the French Communist Party (PCF).