He was elected to the Sierra Grande City Council in 1983, and in 1985 became mayor of the city, serving until 1987. Pichetto married María Teresa Minassian, with whom he had two children. Pichetto was elected to the Provincial Assembly in 1988, and was re-elected in 1991. He was named president of the Río Negro Province chapter of the PJ, and was elected to the Argentine Chamber of Deputies in 1993. He was named Vice-President of the Justicialist caucus in the Lower House in 1997; elections that year resulted in steep losses for the PJ, and Pichetto was not re-elected to a second term. Throughout his career he was a "disciplined" party man, and supported President Carlos Menem's neo-liberal break from the traditionally populist PJ platform during the 1990s. Pichetto took a leading role on legal, justice and penal matters and was appointed to the Council of Magistracy of the Nation, the senior justice advisory body, in 1998, and re-elected in 2001. He sat on the committees on prosecution, the appointment of judges and judicial school, and later chaired the disciplinary committee, and served on the administration and finance committees. Pichetto was elected senator in 2001, his term ending in 2007. He was elected President of the PJ caucus in the Senate on December 30, 2002, and despite his earlier support for the more conservative Menem, became a prominent Kirchnerist. He thus joined the center-leftFront for Victory faction of the PJ in support of President Néstor Kirchner. Pichetto campaigned for governor of Río Negro Province in the 2007 elections. There was some doubt as to whether Kirchner would support fellow Peronist Pichetto, or the incumbent UCR governor, Miguel Saiz, who was a leading supporter of Kirchner from UCR ranks. Kirchner ultimately kept out of the provincial elections, and Pichetto lost to Saiz. Pichetto was re-elected to the Senate that year, however. He retained a key role in the passage of numerous Kirchnerist initiatives through the Senate, though differences arose with President Cristina Fernández de Kirchner over his support of the Law of the Protection of Glaciers in 2010: he was among those who voted for the bill, which passed on September 30 and was later vetoed by the president. Pichetto also objected to the president's support of Río Negro Governor Miguel Saiz of the UCR. These differences cost Pichetto clout in the Senate among fellow Kirchnerists, and contributed to the president's decision against endorsing Pichetto as the PJ candidate for governor in 2011; Carlos Soria won the nomination instead, and was ultimately elected governor. The untimely death of Governor Soria in January 2012 enhanced Pichetto's role in Río Negro politics. He was appointed president of the Río Negro PJ, and his son, Juan Manuel Pichetto, was appointed Minister of Production in the horticulture-rich province - becoming thought of by opponents as a "shadow governor" to Soria's successor, Alberto Weretilneck. From his bench Pichetto accompanied the main projects of the government of Cristina Fernández de Kirchner, such as resolution 125, the nationalization of the AFJP and the media law. After Mauricio Macri assumed the presidency in 2015, Pichetto accompanied several of the legislative projects of the new management. One of them was the voluntary payment of USD 9.3 billion to the vulture funds, which would allow him to leave the country of the default in which he was. He also supported the pension reform carried out in 2017. The interior minister, Rogelio Frigerio, highlighted the role of Pichetto, since it has been fundamental for the approval of more than 200 laws favorable to the government of Cambiemos.
