Indian Prime Minister Narendra Modi, left, gestures to greet party workers after paying tributes at Rajghat, a memorial for Mahatma Gandhi in New Delhi on Monday. (Prakash Singh/AFP/Getty Images)

Narendra Modi became India’s prime minister Monday, a little more than a week after his party scored a decisive victory at the polls.

With the soaring cream-and-red sandstone dome of the president’s house as a backdrop, Modi, 63, took the stage dressed in one of his trademark high-collared vests and read the oath of office in a commanding voice. There were no speeches, and his newly appointed cabinet took the oath with him, as is customary.

Modi was sworn in on the forecourt of the historic residence, Rashtrapati Bhavan, surrounded by more than 3,000 guests and double the number of security staffers to watch over a gathering of world leaders that included President Hamid Karzai of Afghanistan and Prime Minister Nawaz Sharif of Pakistan. Sharif’s attendance was seen as a gesture of goodwill between the rival nations. It was the largest such gathering in the space.

When the votes were tallied May 16, Modi’s opposition Bharatiya Janata Party was the first to win a clear majority in the country’s lower house of Parliament. The BJP came to power on a wave of voter anger and disillusionment against the governing Congress party, whose decade of leadership was marred by a series of corruption and graft scandals.

“It’s the beginning of a new era,” said Mohammad Latief Lone, 38, a businessman from Kashmir who was in town to attend the ceremony.

In the days leading up to his swearing-in, Modi already had demonstrated that he would be a marked change from his predecessor, 81-year-old Manmohan Singh, an economist with a whispery voice who rarely held news conferences.

Modi tweeted about his conversations with world leaders such as President Obama. Earlier in the week, he wept while addressing members of his party in Parliament and spoke about his devotion to “mother” India. The morning of his swearing-in, he appeared at the memorial to the country’s spiritual father, Mohandas Gandhi, and had tea with his new cabinet members, telling them, “We have to perform.”

His official Web site became active Monday. “Namaste!” the new prime minister wrote, evoking the traditional greeting. “As we devote ourselves to take India’s development journey to newer heights, we seek your support, blessings and active participation. Together we will script a glorious future for India.”

Modi, a lover of technology, had run the most costly, tech-
savvy and ambitious political campaign in India’s history, traveling more than 180,000 miles and appearing at more than 5,000 events after he was officially named the party’s choice for prime minister in September. He pledged to lead an honest government that will create jobs and opportunity, a message that went over well with India’s young, increasingly plugged-in and affluent electorate. Modi’s party dominated the 18- to 25-year-olds and urban voters, but it also had support in India’s rural areas.

By contrast, the governing Indian National Congress party — and its chief campaigner, Rahul Gandhi, the son, grandson and great-grandson of prime ministers — was caught off-guard by the “Modi wave.” After the humiliating defeat — the party garnered just 44 seats in the lower house of Parliament — the party president, Sonia Gandhi, admitted this week that leading members had woefully underestimated the “widespread public anger against us.”

For now, it appears, the country has had enough of its dynastic leaders, choosing for its 15th prime minister a man who was the son of a tea seller from one of India’s lower castes. His deprivation growing up in the small town of Vadnagar shaped him, according to his biographer Nilanjan Mukhopadhyay.

“He studied with a kerosene lamp and he said as a child it was traumatic for him,” Mukhopadhyay said. This experience motivated him later, when he became chief minister of his home state of Gujarat, to electrify the majority of the state’s villages, one of his biggest achievements.

As was traditional, his parents arranged a marriage for him as a child. He left his teenage bride. As a young man, he volunteered for the country’s hard-line Hindu nationalist movement, the Rashtriya Swayamsevak Sangh, or the RSS, living frugally and working as a political activist and community organizer. He later moved to the BJP, the movement’s political ally.

He served as chief minister of Gujarat for 13 years, opening his state to foreign investment and building roads and infrastructure. But his bureaucratic career has long been shadowed by questions over his failure to stop the carnage when Hindu and Muslim riots in 2002 left more than 1,000 dead.

For that, the United States denied him a visa. But this year, as it became clear he was India’s choice, U.S. officials began the cautious task of reaching out to the controversial leader. After Modi’s victory, Obama was quick to call and offer his congratulations and invite him to Washington at a “mutually agreeable time.”

“They wanted to convey the need to let the past be the past and let’s build toward a future,” said Ashley J. Tellis, senior associate at the Carnegie Endowment for International Peace.

Thousands had arrived to celebrate the swearing-in in the capital, which echoed with bursts of fireworks. Big-screen televisions were set up at locations around the city so people could watch the ceremony.

“India is going to change for good today,” said Gyan Sharma, 23, a student from the eastern city of Patna. “We waited for this day for so long.”

Jalees Andrabi contributed to this report.