Editing Independent Democratic Union (section)

=== Growth and opposition (1989–2003) ===
[[File:Fundación UDI.jpg|thumb|[[Joaquín Lavín]], [[Jaime Guzmán]] and [[Jovino Novoa]]. c. 1990.]]

By 1990, Guzman was positioned as the leader of the opposition and was one of the harshest critics of the new democratic government, accusing it of softness in the fight against left-wing armed organizations which kept operating in Chile after the restoration of restricted democracy. On April 1, 1991, Guzmán was shot dead by members of the armed left-wing group [[Manuel Rodriguez Patriotic Front]] (''Frente Patriótico Manuel Rodríguez''), after leaving his lecture of Constitutional Law at the Pontifical Catholic University of Chile. He was replaced as senator by the National Renewal candidate for the same constituency, Miguel Otero.

The Independent Democratic Union remained as a minor party in the early years of transition, compared with its ally National Renewal, but over the years managed to win preferences, match and surpass them. In subsequent elections, UDI began to grow noticeably: got 12.11% in a congressional election in 1993, a 14.45% in elections in 1997 and 25.19% in the 2001 elections, when it  became the largest party in Chile, removing that title to the Christian Democrats.

In 1998, when [[Pinochet's arrest and trial|Pinochet was arrested]] in London, the UDI and National Renewal pressed the Frei government to return him to Chile.

In 1999, [[Joaquín Lavín]], the mayor of [[Las Condes]] and member of UDI, was proclaimed as the Alliance for Chile candidate for the presidential election. Even as a relatively new face, a moderate support for Augusto Pinochet and a proposal eminently pragmatic rather than dogmatic, took him to get the 47.51% of the votes against the Concertación candidate Ricardo Lagos on the first ballot, with a difference of about 30,000 votes (i.e., almost one vote per polling place). Finally, in January 2000, Lavín got 48.69% of the votes against 51.31% of Lagos in the second round. That was the highest percentage of the vote received by any right-wing presidential candidate in the 20th century in Chile.

During the first half of the presidential term of Ricardo Lagos (2000–2006), UDI established itself as a relevant political actor of the opposition. Proof of this are the results of UDI in the 2000 municipal elections, the parliamentary elections of 2001, and the  Lagos-Longueira agreement of January 17, 2003 to modernize the State administration and give a consensual political solution to  [[Inverlink case]] and [[MOP-Gate case]], which affected the institutional stability of the Lagos administration. The result of this is the election finance law, high public management law and others. During this period, especially outstanding figure is the party president, [[Pablo Longueira]].

A milestone in the party's image came in 2003 when Longueira reported in a TV interview that he met with relatives of Disappeared Detainees, who saw the party as a serious and reliable institution, through which they could get some of the solutions that Socialist governments had not granted them. Of these numerous meetings, arose the document "Peace Now" ("La Paz Ahora"), which sought to give a sign of national reconciliation.