Together with his brother, Jaime Paz Pereira, he was one of the so-called "political heirs" of the country, a group of younger statesmen whose political careers had been facilitated by their connections to the country's prominent party leaders. In the
2002 general elections, the MIR nominated Paz as its candidate for
Tarija in circumscription 49 (
Avilés-
Méndez), a major stronghold of support for the party. Winning the seat with a comfortable majority, he was elected to represent the district for the
2002–2007 National Congress. Though the
significant social conflicts of the time culminated in the collapse of the traditional party system, Paz's already-established political career survived. When the legislature's mandate was shortened by two years, he was presented by a diminished MIR as its candidate for Tarija in circumscription 46 (
Cercado) for the
2005 general elections, in alliance with
Social Democratic Power of
Jorge Quiroga.
Mayor of Tarija (2015–2020) By August 2006, the inability of the MIR to achieve the required 2% vote threshold in that year's
constituent assembly elections led to the loss of its national registration. With that, Paz joined the ranks of United to Renew (UNIR), led by the ex-
Mirista and Tarija mayor Óscar Montes. In the
2010 regional elections, he headed UNIR's list of councillors in Tarija in support of Montes's bid for a third mayoral term. From 2010 to 2015, he served under Montes as the president of the Tarija Municipal Council and was nominated to succeed Montes as UNIR's mayoral candidate in the
2015 regional elections. Paz swept the race, winning almost 60% of the city's votes. At his mayoral inauguration on 30 May 2015, Montes highlighted that "it has been the MIR, then UNIR, who will govern Tarija for twenty consecutive years". However, Paz's own political project, focused on "rescuing the great
Mirista root" of his father's party, ultimately resulted in the rupture of his alliance with Montes and his departure from UNIR just a year into his term, under accusations that he was trying to "destroy UNIR in order to structure the Revolutionary Left Movement". The culmination of Paz's political project came on 3 April 2019 with the establishment of the
First the People (
Primero la Gente; PG) civic group. With himself at the head, PG aimed at consolidating municipal and departmental sectors into a political alliance whose "ideology is the people". After the
2019 political crisis, Paz's mayoral term was extended by an additional year. However, he cut it short by tendering his resignation on 20 October 2020 to take office in the
Plurinational Legislative Assembly. After four days of debate, the Municipal Council voted to accept Paz's resignation and elected its president, Alfonso Lema, as his successor. In February 2024, the Departmental Prosecutor's Office of Tarija formally charged Paz with alleged irregularities related to the 4 de Julio Bridge, a public works project awarded during his tenure as mayor. The bridge—now widely referred to as the "Million-Dollar Bridge" (
Puente Millonario)—was contracted for
Bs 73.2 million in 2018, during Paz's administration, and according to its contract, was set to be delivered within 900 calendar days, on 25 December 2020. However, several orders extended the deadline well into 2021, at which point fines began to be levied, before Paz's successor as mayor Jhonny Torres terminated the contract with the company Convisa on 12 August 2022 due to the company's failure to meet deadlines. The case was brought forward following a complaint by Torres and is being handled by the Fourth Anti-Corruption Court of Tarija.
Chamber of Senators In the
2019 general elections, PG signed an alliance with the
Christian Democratic Party (PDC), which presented Paz's father, ex-president Jaime Paz Zamora, as its presidential candidate. However, shortly thereafter, Paz Zamora withdrew his candidacy due to internal disagreements with the PDC, leading Paz to shift his support to
Carlos Mesa of
Civic Community (CC). On 3 February 2020, PG finalized an alliance with CC, presenting Paz as the coalition's candidate for first senator for Tarija. During his tenure, Paz was a vocal proponent of census reform in light of the process scheduled for late
2022. In January of that year, Paz presented a bill to establish Departmental Institutes of Statistics (IDEs), aimed at generating departmental, municipal, and regional statistical information. If passed, the legislation would have decentralized the census process —overseen by the
National Institute of Statistics (INE)— which Paz assured would make the 2022 census "a census of the people". Paz also criticized a lack of transparency regarding what preparations and activities were underway to carry out the census. On 7 February, the CC caucus delivered a petition to the
Ministry of Development Planning requesting a report on planned activities. By early March, CC noted that it had not received a response so far. Failing the creation of IDEs due to a lack of time to establish such institutions, Paz also proposed the formation of inter-institutional monitoring committees made up of governorates, municipalities, universities, regional chambers, social organizations, and other relevant groups to guarantee transparency in the process. He was assigned to the following commissions: • Board of the Chamber of Senators (Second Vice President of the Senate; 4 November 2020 – 4 November 2021) • Rural Indigenous Nations and Peoples, Cultures, and Interculturality Commission (President; 10 November 2021–present) ==Presidency (2025–present)==