Sanz was born in San Rafael, Mendoza. He enrolled at the National University of the Littoral, and earned a law degree in 1981. Sanz married Cristina Bessone, and the couple had two children. Following the return of democracy in 1983, he became an adviser to the Governor of Mendoza, Santiago Llaver. He also taught at the National University of CuyoLaw School from 1984 to 1986, and maintained a private practice. He was elected to the UCR Youth Chapter's National Committee in 1987, and as President of the San Rafael Department chapter of the UCR in 1991. He served as a provincial senator from 1993, acting as President of the UCR caucus from 1995, and in 1999 became mayor of San Rafael. Sanz was elected Senator for Mendoza in 2003. He joined the Senate Budget and Domestic Economic Policy committees, and later the Constitutional, Investment, Argentina-Chile relations, and Federal Budget Sharing committees, among others. He was elected ranking member of the Budget Committee, and in 2007, leader of the UCR Senate caucus. Sanz ran for Vice-Governor with Roberto Iglesias in 2007; the ticket, however, was defeated by Justicialist Party candidate Celso Jaque, and finished in fourth place with 10% of the vote. Sanz suffered an automobile accident in March 2008 while driving along the Atuel River in Mendoza; he recovered quickly. Sanz was reelected to the Senate in a landslide in 2009, and in December was elected President of the UCR National Committee. He announced his candidacy on March 2, 2011, for the UCR presidential primary scheduled for April 30. His chief opponent, Congressman Ricardo Alfonsín, was described by Sanz as "an appeal to nostalgia". Sanz withdrew shortly before the April 28 primary, however, and Alfonsín himself placed third in the 2011 general election. The UCR organized the Broad Front UNENpolitical coalition, but it stayed behind in the opinion polls for the 2015 elections. At the radical convention on March 14, 2015 in Gualeguaychú, Sanz and Cobos presented their proposals: Cobos proposed a front of center-left parties, while Ernesto Sanz proposed that the Radical Civic Union lead a broad coalition opposing Kirchnerism for the presidential elections of October 25, which includes the ARI Civic Coalition led by Elisa Carrió and the Republican Proposal of Macri. Cobos, supported by Gerardo Morales and Deputy Ricardo Alfonsin, obtained 114 votes, while the position held by those who supported Sanz reached 186 votes. The UCR joined Macri's Republican Proposal to create the Cambiemos coalition. Macri, Sanz and Elisa Carrió ran for the coalition's primary election, which was won by Macri. Macri won the presidential elections afterwards. It was rumored that Sanz would be the minister of Justice in Macri's cabinet, but he retired from politics for personal reasons.
