The National Reorganization Process ended in 1983. De la Rúa intended to run for President but lost in the primary elections of the UCR to Raúl Alfonsín, who was elected in the general election. De la Rúa ran for the post of senator instead, defeating the Peronist Carlos Ruckauf. He ran for re-election as senator in 1989 but, despite of his electoral victory, the electoral college voted for the Peronist Eduardo Vaca. De la Rúa was elected deputy in 1991 and returned to the senate in 1993. President Carlos Menem, elected in 1989, wanted to amend the constitution to allow him to run for re-election in 1995, which was opposed by the UCR. Alfonsín signed the Pact of Olivos with Menem, negotiating terms to support the proposal. De la Rúa led the opposition to the pact within the UCR, but Alfonsín prevailed in the internal dispute. This damaged the relationship between both Leaders, but helped the party to retain a number of radicals who were against the pact. De la Rúa could not prevent the 1994 amendment of the Argentine Constitution. As a result, Menem was re-elected in 1995. The UCR finished third in the elections for the first time, being surpassed by the Frepaso, a new party composed by former Peronists.