Pratibha Patil, 72, nominated by the Congress-led government, is seen as a shoo-in thanks to support from the ruling coalition and its supporters in the secret ballot to be held on Thursday by an electoral college made up of state and federal lawmakers.

But accusations that Patil shielded members of her family over accusations of murder and abetting suicide have led to charges by the media that her term could be undermined by scandal.

Patil's candidature for the largely ceremonial post was announced as opinion polls showed most Indians favoured a second term for the incumbent president Abdul Kalam, who was the previous Hindu nationalist government's choice.

But Kalam pulled out of the presidential race after the Congress and the opposition Hindu nationalist-dominated alliance could not agree on fielding him for another term.

Though the Congress defended its selection, saying it was giving a woman the chance to occupy the top post in a country where women face heavy discrimination, the opposition said Patil was named due to her loyalty to India's Nehru-Gandhi dynasty.