[1] Part of the prominent Kast family, he served as a member of the Chamber of Deputies from 2002 to 2018, representing District 24 of Peñalolén and La Reina.

He previously ran for president as an independent candidate in the 2017 Chilean general election, and founded the of Republican Action Movement (Acción Republicana) in 2018.

[3] Kast has been labelled as far right, and supports law-and-order messaging and free-market economic policies, while opposing abortion, same-sex marriage, divorce, birth control, euthanasia, and illegal immigration.

[12] Kast studied law at the Pontifical Catholic University of Chile, where he came in contact with the Movimiento Gremialista (Guildist Movement).

As a student, Kast appeared on the 1988 Chilean national plebiscite electoral space, supporting the option to extend Pinochet's rule for eight more years.

He remarked that "[In today's world,] Chileans need God", and said that the state should promote religion in schools by having available teachers for this subject when students choose to have them.

[25] In terms of international relations, Kast proposed closing the border with Bolivia, arguing this measure would allow for a more effective fight against drug trafficking.

In 2018, he called on the government to sever diplomatic relations with France in retaliation for the asylum granted to former guerrilla Ricardo Palma Salamanca.

He opposed the demonstrations that took place during the 2019 Chilean protests, saying that they were not part of a social movement but were instead acts of violence organized by terrorists.

He also proposed banning abortion, fusing the Ministry of Women and Gender Equality, remove Chile from the United Nations Human Rights Council and building more prisons.

[44] Following his success in the first round, Kast garnered the support of most of Chile's right-wing groups, including President Sebastián Piñera.

[33] Internationally, Kast has found solidarity with other right-wing figures, signing the Madrid Charter – a document condemning left-wing groups in Ibero-America authored by the far-right Vox party of Spain – beside other international signatories; Rafael López Aliaga of Peru, Javier Milei of Argentina and Eduardo Bolsonaro of Brazil, the son of President Jair Bolsonaro.

[45] On 30 November 2021, Kast began to make international connections during his campaign, meeting in Washington, D.C., with Republican United States Senator Marco Rubio, the Chilean ambassador to the Organization of American States and at least twenty American business executives invested in Chile, including María Paulina Uribe of PepsiCo.

This followed the results of an internal party consultation where members chose to support Kast with 61.41% of the votes, compared to 6.58% who favored Gabriel Boric.

[57] He has expressed right-wing populist positions[58][59] and support for former dictator Augusto Pinochet,[41] calling for a "firm hand" to govern Chile.

[41][66][67] Kast opposes illegal immigration, abortion, and same-sex marriage in Chile, supporting social benefits only for married women.

"[45] Kast rejects the overwhelming scientific consensus on climate change, downplaying its dangers and denying mankind's contribution to it.