Here are the 10 latest developments in this big story:
The decision to field Meira Kumar, described as "unanimous" by the Left's Sitaram Yechury, has secured the key support of Mayawati's Bahujan Samaj Party. Mayawati, herself a Dalit icon, had indicated that she did not want to be seen as blocking a Dalit candidate's rise to the top office in the country. "UPA nominee for President's post Meira Kumar is more capable and popular than NDA candidate," Ms Mayawati said, according to news agency PTI.
Sources said Nationalist Congress Party leader Sharad Pawar, who had kept the other opposition parties guessing, was asked to speak first and said he favoured fielding Congress leader Sushil Kumar Shinde or economist Bhalchandra Mungekar, both Dalits too.
Leaders of other parties, however, backed Meira Kumar. Sonia Gandhi has appealed to all opposition parties to support Ms Kumar's candidacy. Voting will take place on July 17 and results will be announced three days later on July 20.
After the opposition's announcement, Prime Minister Narendra Modi met BJP chief Amit Shah. Senior ministers Venkaiah Naidu and Anant Kumar were also present.
The BJP and allies now have well over 60 per cent of the vote with the support of several regional parties including both factions of the AIADMK, but the opposition parties say a contest will symbolise "a battle of ideologies".
The anti-BJP front was left considerably diminished by Nitish Kumar, the Chief Minister of Bihar, exiting the bloc to support the BJP's candidate. His partners have requested him to reconsider his decision.
Lalu Yadav said after the meeting, "I appeal to Nitish Kumar to support the daughter of Bihar... We will meet tomorrow and appeal to him to reconsider. One must not do a historical mistake, you've taken a wrong decision". The Congress' Ashok Choudhary too urged to Nitish Kumar to change his mind now that the opposition has picked a Dalit candidate from Bihar in Ms Kumar.
But Pawan Varma of Nitish Kumar's Janata Dal United said there was no question of the party changing its mind. "We have applied our mind and will stick to Kovind... The opposition is now just offering a token fight."
Ram Nath Kovind, 71, was, till his nomination, the Governor of Bihar. Nitish Kumar has said he makes an ideal candidate for Rashtrapati Bhavan. The Chief Minister relies heavily on the support of Dalits in Bihar.
Nitish Kumar's decision to vote with the BJP has put new pressure on his already fragile alliance in Bihar with both the Congress and Lalu Yadav. "Whether he betrayed us or not, that only Nitish Kumar knows. We are in a coalition, we have a government in Bihar and it will continue," said Lalu Yadav.
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