Chapetón joined the National Unity Front party, led by La Paz businessman Samuel Doria Medina, in 2005.
In 2006, Chapetón was elected to the Bolivian Constituent Assembly, a special body charged with rewriting the country's constitution. She represented the 15th electoral district of La Paz, representing part of El Alto.[6] In this position, she backed the demand that the new Constitution require a two-thirds vote in the Assembly, and opposed the text drafted by the Movement Towards Socialism-led majority.[7]
In 2010, Chapetón ran for the post of mayor of El Alto on the National Unity Front slate. She lost this election to Édgar Patana Ticona of the Movement Towards Socialism.
During these five years, she put forward demands upon the national government to support the city of El Alto[8] and was a critic of Patana's administration.[9] At the 2010 congress of National Unity, Soledad Chapetón was elected by consensus as vice president of her party.[10]
In 2014, Chapetón was an unsuccessful candidate for Senator from La Paz department. in the Plurinational Legislative Assembly.
In 2015, Chapetón once again ran for mayor of El Alto, this time on behalf of the Democratic Unity alliance (which joined National Unity and the Democrat Social Movement).[11] In the 29 March 2015 elections, Chapetón won 54% of the vote and obtained a municipal council majority of 6 (of 11) members, allowing her to govern and have her executive decisions approved.[12]
She was inaugurated as mayor on 1 June 2015 and became El Alto's first woman mayor.[13]
