He founded the Broad Front (Frente Amplio), a left-wing political coalition, and was its presidential candidate in the general election of 1971.

Seregni joined the Army of Uruguay in 1931, and was promoted the junior officer rank of Alférez three years later.

He served as Military attaché to the Uruguayan Embassies in Mexico and the United States of America.

In 1971, he made an unsuccessful run for president as the Frente Amplio candidate, receiving 18.3% of the vote (3rd place).

He died on 31 July 2004, of pancreatic cancer,[2] three months before the Frente Amplio won the 2004 presidential elections.