[9][10] Election results were disappointing: the UCiDCC secured only two seats in Congress, one for each party, and the platform's nationwide referent the EDCEE failed to gain any parliamentary representation.

[12] The internal support for each position would be revealed ahead of the 6th Unió congress in September 1977, with the pro-UCD sector being in the minority, resulting in a group of 17 members led by Josep Miró i Ardèvol splitting into the Union of the Christian Democrats of Catalonia–Jacques Maritain Club, which would merge with other parties into the Union of the Centre of Catalonia (UCC) in March 1978 to join into a joint platform with the UCD.

[12] In September 1978, Unió would sign an agreement with CDC to form Convergence and Union (CiU),[14][15][16] an alliance initially appealing to the Catalan centre-left that would end up becoming a big tent platform lasting for the next 37 years.

[12][21][22] From 2013 and until 2015 tensions within the two parties forming the Convergence and Union (CiU) federation reached an all-time high over differences between the positions of the UDC leadership and Democratic Convergence of Catalonia (CDC) leader Artur Mas over the sovereignty process, as well as on the opportunity of forming a joint, pro-independence electoral list with Republican Left of Catalonia (ERC).

[34] In the regional election held on 27 September, UDC would fall short of the 3% threshold to secure parliamentary representation, meaning the party was to be expelled from the Parliament of Catalonia for the first time since 1980.