The five-year term of the current president, Pratibha Patil, ends next month, and federal and state lawmakers are scheduled to elect her successor on July 19. Although a figurehead, the president can play a key role in the event of elections that result in a hung parliament, determining the makeup of the governing coalition.

Mukherjee, 76, is seen as likely to face at least one opposition candidate for the presidency. But both Sonia Gandhi, the head of both the Congress party and the ruling coalition, and Prime Minister Manmohan Singh spoke to the leaders of other parties Friday in a bid to round up support for their nominee.

The ruling coalition struggled for weeks to cobble together a consensus on a presidential nominee, in a tug of war that not only exposed the deep rifts among its allies and raised the prospect of early elections, but also highlighted, once again, the government’s sinking credibility.

Matters came to a head this week when two allied parties suggested Singh, the prime minister, as the nominee, underscoring the lack of trust in his leadership.

On Friday, Gandhi sought to cap the fevered speculation in the capital, exhorting all political parties to unite in support of Mukherjee and noting his “long and distinguished record of public service spanning over five decades.”

But one key government ally, the mercurial Mamata Banerjee, was absent when Mukherjee’s name was finally announced, suggesting that the government will have to lobby its smaller partners hard, not just for their votes in the presidential election but to ensure the coalition’s long-term stability.

Singh’s government has had a bruising relationship with Banerjee in the past year as it battled a slowing economy, rising inflation and a string of corruption scandals and she leveraged her power to scuttle several key economic decisions. This week, the Standard Poor’s rating agency warned that India could lose its investment-grade credit rating, citing weak political leadership and stalled economic reforms in addition to the slowdown in growth.

On Wednesday, Banerjee named Singh as one of her preferred candidates for the presidency.

“This week’s political turmoil has signaled two things — that the country needs to change its prime minister and that in the coming months, the prime minister’s chair will not be above and beyond scrutiny by coalition allies,” said Manisha Priyam, associate professor of politics at Delhi University and a research scholar at the London School of Economics.

Mukherjee’s nomination is likely to precipitate a reshuffle in the government at a time when the economy needs urgent repair. It is not immediately clear who would succeed him as finance minister, but he himself noted that Singh is an eminent economist and added that “under his stewardship we will overcome the temporary crisis” in the economy.

A new regional party that the government is likely to invite into the coalition soon is the Samajwadi Party, headed by Mulayam Singh Yadav, who began his political career as a socialist but in the past decade has embraced free-market capitalism. Priyam said that Yadav might offer support for many of the “pending economic reform decisions.”