The deal was regarded as a milestone in Indo-American relations. But it was opposed by several groups in India, especially the Communist Party, which withdrew support from the governing coalition as the deal was being finalized in 2008.
Brinda Karat, a senior leader of the Communist Party, told AOL News that the cables exposed how Party leaders tried to "whitewash the political crimes that have been committed."
The 2008 civil nuclear agreement was a first step in repairing India-U.S. relations, which had worsened after the U.S. imposed economic sanctions on India for conducting underground nuclear tests in 1998.
The deal was signed under the Bush administration and is still being finessed by the Obama administration, which hosted its first state dinner in 2009 for Indian Prime Minister Manmohan Singh.
The leaked cable, published in The Hindu, said that an Indian political aide showed an American diplomat two chests of cash, allegedly part of a $25 million fund to pay for votes.
Before the vote of confidence on the nuclear deal in 2008, leaders of the main opposition Bharatiya Janata Party, or BJP, produced cash on the floor of the House and claimed that votes had been bought. A subsequent investigation, however, did not lead to any concrete findings.
The cables have brought the issue to the forefront again, according to Karat, who has called on Congress Party leaders to confess and asked the government to conduct criminal prosecutions immediately.
Several analysts in India have expressed concern that the government is bending over backward to accommodate the U.S., which they say is running the show.
The immediate question, however, is whether the Congress-led government will survive. Many observers have suggested that this scandal -- like many others -- will blow over, especially because the allegations are old and the deal has moved forward since then. And WikiLeaks has said that it will reveal more India-related cables, which could distract the public and media with another scandal.
"In normal circumstances, the government would not survive, but we don't live in normal times. ... The corruption has become so deep-rooted," said Prashant Bhushan, a prominent Indian lawyer and activist, who convinced the Supreme Court to investigate the loss of $40 billion from the Indian Treasury in the "2G Spectrum" scam last year.
Still, Bhushan observed that the fragile polity, if hit with another blow, could crumble in the coming months.
Following the recent uproar, Prime Minister Singh told the Indian Parliament that the cables were "speculative, unverified and unverifiable."
"It is unfortunate that the opposition continues to raise old charges that have been debated, discussed and rejected by the people of India," he said last week.
WikiLeaks founder Julian Assange, however, insists that the cables are authentic and that Singh is misleading the public.
"The comments that I've been hearing from Prime Minister Singh, these to me seem like a deliberate attempt to mislead the public by suggesting that governments around the world do not accept this material and that it's not verified," Assange told Indian news channel NDTV.
"That does not mean every fact in them is correct. You have to look at their sources and how they gave this information," he said Monday.
Shoma Chaudhury, the managing editor of Tehelka, an Indian news magazine known for its undercover exposes, argues that the cables have too many "ifs and buts" and are only of "speculative value."
"They are not conclusive by a long shot," she said, adding that the Indian political aide who showed the money to the American official was a junior operative and could have been exaggerating.
While the Congress Party has been mired in a series of billion-dollar corruption scams, its soft-spoken leader is generally regarded as being clean. But in the wake of the new scandal, the BJP has called for his resignation.
It is unlikely that the current scandal will lead to Singh's resignation, according to Vinod Mudgal, who runs a project to improve rural livelihood in India that includes more transparency in governance.
Today, the opposition staged a walkout of a parliamentary session, saying Singh had misled the House in 2008 by claiming that lawmakers had not been bribed.
But the BJP hasn't escaped the scandal unscathed. Shortly after the first revelation, WikiLeaks released cables that suggested the opposition party publicly slammed the nuclear deal but privately reassured the Americans they were OK with it.
"The result of all this is that even the opposition party has no moral authority," Bhushan said.
The BJP has denied engaging in any hypocrisy.