New Delhi, Jul 10 (IANS): The July 19 poll to elect India's 13th president has divided not only the ruling UPA but opposition blocks like the NDA and the Left parties alike.

Within the Congress-led United Progressive Alliance, opposition to its presidential nominee Pranab Mukherjee has come from Trinamool Congress supremo Mamata Banerjee, who thinks the veteran parliamentarian has not done enough for West Bengal, a state she rules.

After ending three decades of Left rule in West Bengal in May 2011, Banerjee has been pressing Mukherjee, who was union finance minister, for a bailout package. With the financial relief nowhere in sight, Banerjee pushed the name of A.P.J. Abdul Kalam for the high office till the former president himself decided to stay out of the contest.

The Congress is hopeful it will somehow manage to convince a mercurial Banerjee to support Mukherjee ahead of the presidential poll.

"This presidential election has affected unity among all the three major political groups," veteran journalist and political observer Kuldip Nayar told IANS.

Mukherjee's candidature divided the Bharatiya Janata Party-led National Democratic Alliance as well.

While the BJP kept waiting for the UPA to announce its candidate, the AIADMK, led by Tamil Nadu Chief Minister J Jayalalithaa and the Biju Janata Dal, led by Odisha Chief Minister Naveen Patnaik, both of whom are former NDA constituents, took the lead and nominated former Lok Sabha Speaker Purno A. Sangma as their presidential nominee.

As the BJP pondered whether to support Kalam or Sangma, its key allies Janata Dal-United (JD-U) and Shiv Sena broke ranks with the alliance and announced their support for the UPA nominee saying they did not want a contest for the top constitutional post.

"We nicely agreed to disagree," JD (U) chief Sharad Yadav told IANS.

With Kalam opting out of the race, the BJP was left with no choice but to back Sangma, hoping the move would help it rope in the AIADMK and the BJD to strengthen the NDA ahead the 2014 general elections.

Battling indecision, the BJP also did not want itself to be seen supporting the UPA's presidential candidate.

The issue has divided the Left too.

"Mukherjee's candidature has divided both the NDA and the Left," Congress leader Mani Shankar Aiyar told IANS.

While the Communist Party of India-Marxist and the Forward Bloc are supporting the UPA nominee, the Communist Party of India and the Revolutionary Socialist Party have decided to abstain from the contest.

"We have decided not to support either Mukherjee or Sangma," CPI national secretary D Raja told IANS.

According to an article written by CPI-M general secretary Prakash Karat for People's Democracy, the party mouthpiece, the party is supporting the UPA nominee "to prevent the BJP from putting in place a constitutional head of state who would be amenable to the influence of the Hindutva forces, a development that would be inimical to the secular democratic principle of the constitution."

The RSP, said the article, has often refused to support the Congress nominee since 1992.