Marika Mitsotaki, the wife of former premier and New Democracy leader Constantine Mitsotakis, died in the early hours of Sunday morning.
Mitsotaki was 82 and had been hospitalized two weeks ago. She died of multiple organ failure.
Her daughter, Dora Bakoyannis, is the leader of the small, liberal Democratic Alliance. She had been in Crete, where she was due to vote, but flew back to Athens early on Sunday.
Mitsotaki was also the mother of New Democracy candidate Kyriakos Mitsotakis.