The supporters of Arturo Alessandri weren't included. It was a party related to Carlos Ibáñez del Campo. As time went by, its members split up to form other parties. With the downfall of Ibáñez all groups gathered up again, led by Alessandri to create the Liberal Party (October 1930) with a mutual party platform. In this process, the ULP merged into the LP during the VI Convention (October 1933) of the LP.
The original version of this article draws heavily on the corresponding article in the Spanish-language Wikipedia, which was accessed in the version of June 7, 2007.