That Karat—the feisty, British-educated 59-year-old general secretary of the Communist Party of India (Marxist), or CPI-M—has come to dominate New Delhi’s agenda is remarkable, given that he has little national following, has never held elected public office and holds ideas that were already out of date 15 years ago, when most communist systems came crashing down. India’s leftists, moreover, are widely reviled for their obstructionism on the national level and their violent misrule in West Bengal, the CPI-M’s power base. Yet Karat (who was unavailable for comment) has nonetheless wielded outsize influence for more than three years. That’s because the Congress Party-led coalition has just a razor-thin majority in Parliament, which has forced it to lean on Karat for support, turning him into a kingmaker and a potential spoiler.

Karat has played that role to the hilt. He and the left “have frustrated Singh at every turn,” says a Western diplomat in New Delhi. As Singh himself complained in October, “It has become difficult at times for us to do what is manifestly obvious.”

Singh’s frustration is easy to understand, for it is obvious what New Delhi should be doing. If it hopes to continue growing, India needs more of the economic reforms Singh initiated as Finance minister in 1991. It needs a more dependable and cleaner power supply. And it must make common cause with the industrialized West, in order to carve out more influence on the world stage. The nuclear deal could deliver these last two things.

Yet Karat doesn’t agree. In his view, liberalizing the economy and joining world trade would simply give Washington, the imperialist bogeyman, greater control over his country. As for the impending nuclear deal, never mind the argument—backed by a vast array of Indian scientists, energy experts and military leaders—that it represents Singh’s crowning achievement, will end a three-decade-old ban on international nuclear-energy cooperation and will usher in a strategic alignment with America. Karat sees only danger. “History won’t forgive us if we collaborate in tying our destiny to the United States in perpetuity,” he declared in a speech this September.

Such views may not be popular anymore, but Karat nonetheless speaks from a position of strength. His power dates from 2004, when inconclusive general elections elevated the communists from obscurity. Although they have controlled West Bengal for 30 years and Kerala on and off, the left had never played a big part on the national stage. But three years ago Congress won just 147 out of 543 seats—barely besting the incumbent Hindu nationalist Bharatiya Janata Party (BJP), which got 139 seats. The four leftist parties took advantage of the weak opposition to score an unprecedented 62 seats. This forced Congress, under Singh and Sonia Gandhi, to come calling when they set out to cobble together a government. The communists agreed to support the 16-party coalition, but refused to accept a cabinet seat—a shrewd move that gave Karat and his associates the ability to bring down the government at any moment while freeing them from the responsibilities of ruling.

Since then, Karat has made the most of his leverage. He has pushed Singh and Gandhi to better help India’s poor—the many millions left out of the BJP’s business-friendly “India Shining” campaign—through generous aid programs. Chief among them: the Congress Party and the communists jointly sponsored a National Rural Employment Guarantee Act in 2005 that promises one member of each poor rural family 100 days of work per year, at a minimum wage of about $1.50 a day. The program has targeted some 350 million impoverished Indians, one third of whom must be women.

Karat and Singh share a real sympathy for India’s unfortunates, stemming from both men’s humble upbringings. Both leaders are also known for their honesty, integrity and intelligence. The two were top students growing up, and both went to university in the United Kingdom (Karat to the University of Edinburgh; Singh, to Cambridge and then Oxford).?But the similarities end there. Above all, Karat is known for his ideological purity. He “is dogmatic and puritan and Stalinist in approach,” says Ramesh Dikshit, who was a student leader with Karat after he returned to New Delhi.

Such dogmatism has given the government fits. Karat has managed to block Singh’s attempt to privatize inefficient state-owned industries, has killed labor-market reforms and has prevented the opening of the banking and insurance sectors, as well as the booming and lucrative retail market, to foreign investment. Still, the real focus of Karat’s ire has been the nuclear agreement with the United States, which New Delhi painstakingly negotiated over three years.

The prime minister sees the deal as vital to India’s emergence as a world power. It is also key to sustaining its economic progress. As the nation has boomed, electricity production has lagged, leading to frequent power cuts in homes and industry; nearly half of rural India still lacks access to a reliable power supply. Nuclear energy is not a magic bullet, but Singh thinks it can help, and aims to increase India’s nuclear power production from 3 percent to 10 percent of total energy production by 2020. For that to happen, however, he has to end America’s 33-year-old embargo on access to nuclear fuel and technology, in place since Delhi first tested a nuclear device in 1974.

In this pursuit, Singh found an understanding and willing partner in George W. Bush, with whom he’s worked closely since first explaining his vision at a meeting at the United Nations in September 2004. Bush was immediately enthusiastic and promised to see what he could do. When the two men met again, less than a year later in Moscow, Bush, according to a senior Indian government official, asked Singh how specifically he could help. Singh asked him to end the sanctions, and Bush agreed to try. In several short weeks, Indian and U.S. negotiators hammered out a deal under which Washington would lift the sanctions and recognize India as a nuclear-weapons state and supply it with nuclear fuel and technology—including reactors.

India, in return, pledges to separate its military and civilian nuclear facilities and put the latter under international oversight. But “it’s a win-win for us,” says Kapil Sibal, the minister of Science and Technology. “I don’t see any downside.” Indeed, India gets to keep its nuclear-weapons program free of international inspection. Once India negotiates a safeguards agreement with the International Atomic Energy Agency, gets approval from the international Nuclear Suppliers Group, and the package is ratified by the U.S. Congress, India will be able to ramp up nuclear-power production dramatically.

But that won’t happen unless Singh can keep the left onboard. In August 2006, after a debate in Parliament, the communists listed nine specific concerns with the agreement, including securing a guaranteed supply of nuclear fuel. Singh promised the communists he’d address the issues, and the prime minister duly raised them during a meeting this past June in Berlin with Bush, who helped resolve them. By September of this year, Singh had worked out a new version of the deal, which had been specifically crafted to meet many of the left’s objections. Yet the left still dug in its heels, and it gradually became clear that any deal worked out with George Bush’s America would not fly with Karat.

Fed up with the opposition, the normally soft-spoken Singh dared the left to bolt last August, saying, “If they want to withdraw support, so be it.” Not to be outdone, Karat threatened “heavy political consequences” if Singh rammed through the deal. In October, Karat upped the ante, saying the real problem with the deal was not the technical issues but the U.S. design to “encircle” China.

Singh’s coalition, which has been struggling in the polls, was in no mood to face early elections and began to waver. The prime minister, feeling betrayed, reportedly threatened to resign. Karat stayed on the offensive, and speaking at a party gathering on the 90th anniversary of the Bolshevik revolution, he vowed, “We shall not rest until strategic ties with the U.S. are snapped.” Karat’s opposition may have been more than ideological. “They [the communists] thought the P.M. in a fit of anger would resign,” says one senior Indian government official. “They were trying a coup.”

The purported coup failed and the prime minister decided to stand firm. But his stance has cost him personally. “He’s tired, worn down and depressed,” says the senior government official. “This has taken a lot of his energy.” Singh also feels let down by his week-kneed allies and his boss, Gandhi, who never provided energetic support for the deal. “Her support has not been vigorous,” says Pratap Bhanu Mehta, president of the New Delhi-based Center for Policy Research, pointing out that Gandhi never engaged in the kind of behind-the-scenes arm-twisting necessary to solidify support. Many analysts think that’s because her paramount aim is to keep the Congress Party in power at all costs, paving the way for her 37-year-old son, Rahul, to take over the reins of the party and government. To make that happen, says the senior government official, she needs to keep the left happy, since Congress and the BJP have roughly equal weight in Parliament and the regional parties tend to drift from side to side.

Ironically, Karat’s communists are today in a weaker position than they acknowledge. Analysts predict they would lose seats in a new election: Karat’s national standing has plummeted as a result of his obstructionism. And the party’s longtime power base in West Bengal has recently been eviscerated by a series of stupid and violent blunders there. After the party’s unquestioning support for militant trade unions sent the economy there into a tailspin, local CPI-M leaders embarked on a Chinese-style reform drive in 2000, including the establishment of special economic zones that would cut red tape, slash taxes and offer breaks from the state’s worker-friendly labor laws. This lured in a bevy of corporations but also led to massive protests by subsistence farmers who refused to sell the land on which the SEZs were to be established.

The government responded with overwhelming force last March, sending armed thugs and police to attack villagers in Nandigram who were protesting plans to build a chemical complex there. Fourteen people were killed and more than 160 injured. Although the local government scrapped the project, unrest continued to simmer. Earlier this month armed CPI-M cadres again raided Nandigram, killing six more people, raping several women and displacing nearly 5,000 people through intimidation and arson. Adding oil to the fire, the local communist leaders then seemed to endorse the violence, calling it “morally and legally” justified. Nationwide protests followed. This time even sympathetic intellectuals began to condemn the CPI-M in print.

In the wake of these events, Karat has recently backed off from brinksmanship over the nuclear deal, hoping to persuade the Congress Party not to intervene in the local conflict. In mid-November, Karat’s men even agreed to allow the government to begin negotiating the safeguards agreement with the IAEA—a previous redline.

Such flip-flopping may only further hurt the communists’ already low national standing, though they are likely to retain enough seats in the next election to stay politically relevant. Of course, Karat can still torpedo the deal once the safeguards agreement is finalized. If he does, however, the impact could be devastating. India will have blown its best shot ever at abandoning the mistakes of the past and setting itself on a brave new path forward. And the real losers, as always, will be India’s poor, those still waiting for the economic miracle to reach them. The communists, in a bitter irony, will have betrayed the same unfortunates they are supposedly dedicated to helping.