[1][2] He was President of Uruguay, as an interim chief executive, between February and March 1985 and between the resignation of Gregorio Álvarez and the accession to the office of Julio María Sanguinetti.

Defenders of the political arrangement whereby Addiego became president were able to point out that it enabled Sanguinetti to receive the transfer of office from a civilian (Álvarez being a General).

To international observers, the public relations aspect of what was billed as Uruguay's transition to democracy was enhanced by the increased psychological distance between Sanguinetti and Álvarez.

Furthermore, it is an undoubted fact that many members of Sanguinetti's Colorado party supported rule by decree, both in the preceding 12 years and, indeed, during the extra-parliamentary régime of Gabriel Terra during the 1930s.

In this, he resembled several late 19th-century interim presidents, who served as temporary heads of state as a result of sometimes complex, bargaining procedures between prominent, political power-brokers.