Rao suffered cardiac arrest when he was getting into his car at Eluru to embark on a campaign for the upcoming Gram Panchayat elections, family sources said. He was 66.
A key aide of Union Minister K Chiranjeevi, Rao began his political career in the Telugu Desam Party (TDP) and was elected to the Assembly from Chintalapudi constituency five times in a row from 1983.
He was a Minister in the cabinets of N T Rama Rao and Nara Chandrababu Naidu and held important portfolios like Agriculture and Major Industries.
In 2008, Rao quit TDP and joined Praja Rajyam Party (PRP) floated by Chiranjeevi and remained the actor-turned- politician's key aide. Rao lost the 2004 and 2009 Assembly elections. Upon the PRP's merger with the Congress, Rao was appointed the APCC spokesman.
TDP President Chandrababu Naidu expressed grief over the passing away of his former party colleague. Chiranjeevi expressed shock over the sudden demise of his aide.
Several other leaders of the Congress, including Chief Minister Kiran Kumar Reddy and his deputy Damodar Rajanarasimha, also condoled Rao's death. Reddy spoke to the departed leader's family members and consoled them.