NEW DELHI — Opposition leader Narendra Modi will be India’s next prime minister, winning the most decisive election victory the country has seen in more than a quarter century and sweeping the long-dominant Congress party from power, partial results showed Friday.

Modi’s Hindu nationalist Bharatiya Janata Party was winning in 279 seats in the lower house of Parliament, beyond the 272-seat majority needed to create a government without forming a coalition with smaller parties, the Election Commission said.

Full results were expected later in the day but it was unlikely there would be a significant reversal.

The outcome was a crushing defeat for the Congress party, which is deeply entwined with the Nehru-Gandhi political dynasty that has been at the center of Indian politics for most of the country’s post-independence history.

“India has won!” Modi tweeted with a note of triumph after a slick and well-financed campaign that promised a revival of economic growth and took advantage of widespread dissatisfaction with the scandal-plagued Congress party.

At BJP headquarters in New Delhi, party workers handed out sweets, set off firecrackers and danced in the streets.

In Gujarat state, where Modi has been chief minister for more than a decade, jubilant supporters and a frenzied media surrounded Modi as he visited his mother and touched her feet, a traditional gesture when Hindus seek the blessings of an older relative. His mother then marked his forehead with vermilion and fed him sweets.

The last time any single party won a majority in India was in 1984, when an emotional nation gave the Congress party a staggering victory of more than 400 seats following the assassination of then-Prime Minister Indira Gandhi.

The overwhelming victory gives Modi, a 63-year-old career politician, a strong mandate to govern India at a time of deep social and economic change. India is in the throes of rapid urbanization and globalization just as the youth population skyrockets — with many new voters far less deferential to traditional voting patterns focused on family lineage and caste.

For the young Indian voters, the priorities are jobs and development, which Modi put at the forefront of his campaign.

Congress, which has been in power for all but 10 years of the country’s history since independence from Britain in 1947, has been plagued by repeated corruption scandals. Friday’s results showed Congress leading in only 42 seats, its worst showing ever.

The leader of the Congress campaign, 43-year-old Rahul Gandhi, failed to inspire public confidence. He was seen as ambivalent at best over winning a job held previously by his father, grandmother and great-grandfather.

“I wish the new government all the best,” Rahul Gandhi told reporters Friday afternoon, adding that he held himself responsible for the party’s losses.

Immediately after his appearance, his mother, Sonia Gandhi, the president of the party, took the stage and said she assumes responsibility.

The two took no questions after their brief remarks.

Rahul Gandhi, who first won a seat in Parliament in 2004, has been viewed as prime-minister-in-waiting for his entire political career, though he never appeared comfortable in the role. When he finally gave the first television interview of his political career earlier this year it made for dull, uninspiring viewing full of vague promises.

In sharp contrast, Modi was quick to publicly mock the Gandhi scion, often referring to the Congress as a “mother-son” government.

There was a record turnout in the election, with 66.38 percent of India’s 814 million eligible voters casting ballots during the six-week contest, which began April 7 and was held in stages across the country. Turnout in the 2009 general election was 58.13 percent.

“In the history of independent India, no political party has defeated the Congress party with such a wide margin,” BJP President Rajnath Singh told a news conference that opened with the blowing of a conch shell, a traditional start to most Hindu rituals.

Modi’s campaign was seen by many as a media and marketing coup for a man whose background ties him to bloodshed in Gujarat, where communal rioting in 2002 left more than 1,000 people dead, most of them Muslims. Modi is accused of doing little to stop the rampage, though he denies any wrongdoing and has never been charged with a crime.

Modi was denied a U.S. visa in 2005 for alleged complicity in the riots, although as prime minister he would be virtually assured a visa.

The Obama administration started mending fences in February, when, for the first time in Modi’s decade-long tenure as the top official in Gujarat state, the U.S. ambassador met with him. Still, Modi, a Hindu nationalist, is widely seen as a divisive figure and critics have often questioned whether he can be a truly secular leader in a country with many faiths.

But Modi focused on promises of a revival in economic growth, taking advantage of widespread dissatisfaction with the Congress party.

At one point Friday, the benchmark Sensex stock index rose as much as 6.1 percent on news of the BJP’s strong showing before closing 0.9 percent higher than Thursday.

Sreeram Chaulia, a political analyst and dean of the Jindal School of International Affairs, said the BJP’s image as a purely capitalist, pro-business party resonated across India. That image contrasts with Congress, which is considered more of a welfare party, mixing capitalist reforms with handouts for the poor.

“A lot of ordinary people believed in (Modi’s) message and wanted to give him the strong mandate he was seeking, to see if he could really change things in India,” Chaulia siad. “There has been growth in the middle class, so of course why have they punished the incumbents? Because they want more, obviously, something more than subsistence. They want upward mobility.”

Modi managed to hammer away at Gandhi — specifically the perception that he is nothing more than a feudal prince from a family that views ruling the country as its birthright.

In sharp contrast to the street parties outside the BJP office, a sober scene played out in front of Congress headquarters, where few showed up despite barricades erected to protect supporters from passing road traffic.

Jairam Ramesh, India’s rural development minister, lamented his party’s defeat but said Congress will survive.

“I admit that in 2014, the result is worse than our worst-case scenario,” he said. “But the Congress party has a deep reservoir of strength.”

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