NEW DELHI (Reuters) - Indian opposition leader Rahul Gandhi appointed his charismatic sister to a senior party position on Wednesday that officials say will energize the campaign to oust Prime Minister Narendra Modi in the national election expected in a few months.

FILE PHOTO: Priyanka Gandhi Vadra, daughter of India's ruling Congress party chief Sonia Gandhi, adjusts her flower garlands as she campaigns for her mother during an election meeting at Rae Bareli in the northern Indian state of Uttar Pradesh April 22, 2014. REUTERS/Pawan Kumar/File Photo

Priyanka Gandhi Vadra, 47, has campaigned for the Congress party in previous elections to help her brother, but largely stayed in the wings, letting her brother fully take the mantle of the Nehru-Gandhi dynasty that ruled India for most of its post-independence era.

Bearing a striking resemblance to her grandmother and former prime minister Indira Gandhi - who was known as “India’s iron lady” - Vadra will be a Congress general secretary for Uttar Pradesh, the most populous state and key to the national poll.

“We will play politics on the front foot,” Rahul Gandhi told reporters. “I am very happy my sister, who is very capable, will work with me.”

Congress is trying to build an opposition alliance against Modi’s ruling Bharatiya Janata Party (BJP), which faces grumbling over a lack of jobs and a weak farm economy.

Modi remains the frontrunner, but his re-election is no longer assured after the BJP suffered a string of defeats in state elections last month.

If the Congress and regional parties fight the election in U.P. in an alliance, they could take as many as 75 parliament seats of the 80 at stake in the state, a poll published by India Today on Wednesday showed. India’s lower house of parliament has 545 members.

Vadra will oversee the eastern part of Uttar Pradesh state, including the city of Varanasi, one of Modi’s political constituencies, the Congress party said in a statement.

COMBATIVE STYLE

“This will have an electrifying effect across the country, not just in Uttar Pradesh,” said Jitin Prasada, a Congress party leader.

Vadra is seen as a more natural campaigner and a bigger draw than her brother, who appeared wooden during the last election.

More recently, Rahul Gandhi has adopted a combative style, sniping at Modi with accusations over graft, abuse of power and a divisive brand of politics.

Vadra’s entry into full-time politics could give more ammunition to Modi who has positioned himself as the son of an ordinary tea-seller against the dynastic politics of Congress.

On Wednesday, Modi spoke about the Congress party’s obsession with the Nehru-Gandhi dynasty.

“For some family is the party. But for the BJP, party’s family,” he told party workers.

The siblings’ great grandfather, Jawaharlal Nehru, was India’s first prime minister following independence from Britain in 1947. Their grandmother, Indira Gandhi, succeeded him after a brief interval. After she was assassinated by her Sikh bodyguards in 1984, her son, Rajiv Gandhi, took over as premier.

Rajiv was killed by an ethic Tamil suicide bomber while campaigning for a general election in 1991.

His Italian-born widow, Sonia, initially resisted calls to enter politics before taking the plunge and lifting Congress’ flagging fortunes under her family’s brand name.

Sonia Gandhi stepped back as her son took the reins of the party.

“We want to congratulate the Congress party on this move. Basically they are saying Rahul has failed, now they need his sister,” said BJP spokesman Sambit Patra.