Troncoso was a member of the Independent Democratic Union (UDI) until July 2020, when she resigned from the party following her vote in favor of the bill allowing the withdrawal of ten percent of pension funds from individual capitalization accounts.[2]
In the 1996 municipal elections held on October 27, she was elected councillor of the commune of San Vicente de Tagua Tagua, obtaining 2,113 votes, equivalent to 10.64 percent of the validly cast ballots.
In the municipal elections of October 2000, she was elected mayor of San Vicente de Tagua Tagua representing the Independent Democratic Union, receiving 7,529 votes, equivalent to 35.31 percent of the total. She was re-elected in 2004 with 9,621 votes, corresponding to 45.50 percent, and again in 2008 for a third consecutive term with 49.84 percent of the vote.
In the 2012 municipal elections, she ran for a fourth term as mayor but obtained 28.50 percent of the vote, which was insufficient for re-election.
In the following year, during the first direct elections for Regional Councillors, she ran as a candidate of the Independent Democratic Union for the Province of Cachapoal, obtaining 10,712 votes, equivalent to 7.98 percent of the total, and was not elected.
In June 2016, she participated in the Chile Vamos primary elections to become the coalition’s candidate for mayor, defeating the Renovation National candidate with 2,852 votes, equivalent to 72.09 percent of the ballots cast. However, in the municipal elections held in October 2016, she obtained 6,728 votes, corresponding to 39.52 percent, and was not elected mayor.
In the parliamentary elections of November 2017, she was elected deputy for the 16th District of the Libertador General Bernardo O’Higgins Region, representing the Independent Democratic Union within the Chile Vamos coalition. She obtained 7,987 votes, equivalent to 5.82 percent of the validly cast ballots, and served for the 2018–2022 legislative period.[2]
She did not seek re-election in the 2021 parliamentary elections.
