While in the Senate, Díaz de la Portilla served as President Pro Tempore from 2002 to 2004, and later became Majority Leader in his final two years. He chaired the Domestic Security Committee in 2003, and he also chaired the Communications, Energy and Public Utilities Committee.
On May 3, 2017, Díaz de la Portilla filed to run for the Florida Senate from the 40th district, to fill the vacancy left by Senator Frank Artiles' resignation. Portilla Lost to Jose Felix Diaz by over 30 points.
Díaz is one of the four children of Cuban exiles Miguel Ángel Díaz-Pardo and Fabiola Pura de la Portilla-García. His paternal great-grandfather served in Cuban Senate, while two of his sons served simultaneously in the Cuban House of Representatives. His maternal great-grandfather served as Cuban Minister of Justice.
Renier Díaz de la Portilla served two stints on the Miami-Dade County School Board (1996–1998 and 2006–2012). He also succeeded Alex in the House of Representatives, serving one term from 2000 to 2002.