Mr. Gandhi traverses the country, often on secret trips, to recruit as many as 10 million new youth members. His job is also to try to take back crucial strongholds like Uttar Pradesh, in the north, which his family claims as its home base but which the Congress Party does not control.

Most Indian political parties are internally undemocratic and often dominated by political dynasties, none more famous the Gandhi clan. But Mr. Gandhi has also insisted that the party’s youth organizations hold internal elections for posts and operate as meritocracies.

He also has succeeded far more than other Indian politicians in tapping into the hunger for generational change in India, analysts say, and has positioned himself as a change agent for the future, despite his obvious debts to India’s political past. He is trying to bypass the identity politics of caste and appeal to young people of all backgrounds. “We youth are with Rahul!” said Manonit Garharabari, 23, at the rally. “The whole youth is with Rahul. We seen an internal strength in him.”

Mr. Gandhi is omnipresent in the media, and his face is plastered on untold numbers of billboards and political posters. His public image is as a humble, serious man, if somewhat shy, even as his name invariably tops polls ranking the country’s “hottest” or “most eligible” bachelors. Yet he almost never grants interviews, including for this article, and only occasionally conducts news conferences. Reporters are often tipped to his appearances at one village or another but often all they get is a photograph  which inevitably appears in newspapers around India.

Image A helicopter carried Rahul Gandhi above a rally in May in Ahraura, India. It is rumored that he might become prime minister. Credit... Keith Bedford for The New York Times

His daily life is cloaked in secrecy, which makes it an irresistible if elusive topic for the Indian media. One news station ran a lengthy report after obtaining a short video clip of Mr. Gandhi riding his bicycle in New Delhi. Mr. Gandhi confirmed in 2004 that he had a Spanish girlfriend, but whether they remained a couple was unclear.

His advisers say his low profile reflects his desire not to overstep the authority of his organizational position while the secrecy is rooted in security concerns. His grandmother, Indira Gandhi, was assassinated, as was his father, Rajiv Gandhi. (The family is not related to Mohandas Gandhi, considered the father of modern India. Rahul Gandhi’s great-grandfather was Jawaharlal Nehru, the first prime minister and another founding father.) His official residence in New Delhi is heavily fortified and he traveled to the rally in Ahraura with a special black-clad security detail.