Priyanka Gandhi joined the election campaign in the country's most politically important state, Uttar Pradesh on Tuesday, injecting sparkle into a tightly fought race and overshadowing her brother Rahul Gandhi, heir-apparent of the Nehru-Gandhi dynasty.

Vivacious and bearing a striking resemblance to her grandmother and former prime minister Indira Gandhi - who was known as ‘India's iron lady’ - 40-year-old Priyanka has until now stayed mostly in the wings of the political fray.

Though her mother, Sonia Gandhi, is at the helm of the ruling Congress party and her elder brother, Rahul, is being groomed to take over, Priyanka was staying away from the political action.

Rahul Gandhi has laid a heavy stake on the party's performance in Uttar Pradesh state's February-March staggered vote, a crucial milestone to general elections in two years.

Rahul's campaigning in a poverty-stricken corner of Uttar Pradesh drew scant media attention on Tuesday as news networks focused on his sister, whom many see as the natural leader of a party that has long passed its dominance of Indian politics.

But Priyanka made it clear that she was campaigning in the populous state of 200 million people for her brother.

"If Rahul wants me to campaign, I'll campaign," she said with a broad smile at an impromptu roadside meeting with out-of-work factory workers in her mother's parliamentary constituency, Raebareli.

"I'll do whatever he requires me to do."

Speeding along in a long convoy of vehicles that bounced from meeting to meeting, kicking up dust-clouds along potholed roads, Priyanka's whirlwind election tour is for now limited to the family's traditional stronghold in the state.

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As she mingled comfortably with the crowds, Priyanka hinted that she might be willing to step into politics full time, which would delight many leaders and grassroots activists in a party that was thrown into disarray last year when her mother unexpectedly underwent surgery for an undisclosed illness.

"He knows to what extent he requires me," Priyanka said of her brother Rahul, when asked if she would consider standing in future elections.

The Nehru-Gandhi dynasty, which has enjoyed a status close to royalty since India won independence in 1947 and has spawned three former prime ministers, two of whom were assassinated, Indira Gandhi and Rajiv Gandhi.

"The people of Amethi have come to appeal to her that she should come into active politics, we are all waiting for her," said supporter Babita Singh, who was waiting with a group of women in bright saris to see Gandhi.

"The entire country will change. Throughout India there will be a Congress wave," she said as her friends sang songs feting the leader. "We see Indira reflected in her."

Not everyone was so unconditionally supportive.

Ranjana Tiwari, a union leader, flagged down her convoy to demand the Gandhis' help to re-open a carpet factory. "If there is no work, they don't get our vote," she told the media at the abandoned plant.

Many supporters believe Priyanka can take on Uttar Pradesh's current chief minister Mayawati.

The Congress party needs to win back the support of former untouchable castes and Muslim voters if it is to increase its clout in Uttar Pradesh, where it now holds just 22 of the 403 seats in the state assembly.

Elections are hard to predict in Uttar Pradesh, with its large population of swing voters organized by religious and caste blocks. Rahul has drawn large crowds at his rallies, but he has an uphill battle in a state that his party has not ruled for decades.

The election is a four-way race and analysts say the best Congress can hope for is to form a coalition government with another party, especially since neither Rahul nor Priyanka are being promoted as the state's next chief minister.