NEW DELHI (AFP) - Mr Rahul Gandhi, the next in line in India's top political dynasty, has been handed the keys to power, but his political abilities and policy convictions remain largely an open question.

Mr Gandhi was named vice-president of the ruling Congress party on Saturday at a ceremony that saw senior leaders openly weeping. Tributes hailed him as "the heartbeat of young people" and even India's answer to Mr Barack Obama.

In his decision to accept the post, the 42-year-old who has spent a lifetime in the corridors of power appeared to signal willingness to follow in the footsteps of his great-grandfather, grandmother and father as prime ministers.

Until now the Cambridge and Harvard-educated bachelor, often spotted in upmarket nightspots and restaurants in the capital, had refused repeated offers of cabinet positions and entreaties to take a bigger role in the party.

"I will fight for the people of India with everything I have," he promised party members, who see the Gandhi dynasty as the force that binds together India's only national secular party.

"Congress party is now my life," he added late on Sunday at the end of a strategy meeting in the city of Jaipur before national elections scheduled for early next year.

But Rahul has spent many years seemingly unsure of his own future, first going into business management in London before returning to India and winning the family parliamentary seat of Amethi in Uttar Pradesh state in 2004.

He has since concentrated on a low-profile mission of reviving the Congress youth wing, while undertaking heavily publicised visits to marginalised and seemingly wronged people such as tribal groups threatened by mining.

His occasional trips to stay overnight with low-caste families and even rare journeys on Delhi's metro system are covered intimately by the Indian media, ensuring him constant and generally positive publicity.

But his refusal of greater responsibility and his aloof style - he almost never gives interviews and is a reluctant public speaker - has raised consistent questions about his appetite to be prime minister.

A US diplomatic cable written by the American ambassador and leaked in 2011 stated that Rahul was "widely viewed as an empty suit".

For all these reasons, his decision to become number two in the party behind president Sonia Gandhi, his mother, is seen as a watershed moment.

"There is one subject now closed for discussion. Mr Rahul Gandhi will lead the party in the next campaign, and thereby claim the prime ministership if the electorate makes this a possibility," wrote commentator M.J Akbar.

While his leadership style and thoughts on important issues such as economic liberalisation or relations with Pakistan remain something of a mystery, his political achievements so far are also mixed.

He is an intermittent attendee in parliament, appearing on just 41 per cent of days since elections in 2009 and taking part in only one debate, data from parliamentary think-tank PRS Legislative shows.

When left jointly to handle the party during an absence by his mother in 2011, the government lurched into a crisis sparked by an anti-corruption crusade by a 74-year-old former truck driver.

Most significantly, he spearheaded campaigning for local elections in the northern state of Uttar Pradesh last year, giving hundreds of stump speeches and helping pick candidates.

Congress - the dominant force in Indian politics since independence - suffered a landslide defeat, winning only a small increase on their miserly tally of 2007 and leading to murmurs that Rahul's sister Priyanka might be a safer bet for the future.

"Having already wielded the power, Rahul will now have to acknowledge responsibility," the Indian Express said in an editorial on Monday.

"He no longer has the option of parachuting in and out of situations at will and evading questions about failure or follow through."

The biggest challenge will be to energise his party ahead of elections expected in early 2014 after a difficult second term in office for the Congress-led coalition government.

The next elections could also see the power of the Gandhi name tested by hardline Hindu nationalist Narendra Modi from the opposition Bharatiya Janata Party.

Mr Modi, the son of a tea-stall owner who has been thrice elected as chief minister of the booming western state of Gujarat, would relish emphasising his own very different personal story.