PM Modi's depiction of the 47-year-old as an undeserving "prince" has helped sideline Mr Gandhi since then, during which time the Congress has also suffered some of its worst ever state election results.
But this year the economy has stumbled, and Congress politicians hope a round of state elections, beginning in PM Modi's home state of Gujarat, offer them and their leader a shot at revival ahead of the next national election in 2019.
Mr Gandhi will soon take over as Congress president from his 70-year-old mother, Sonia Gandhi, a symbolic promotion that three Congress leaders said they hoped would free his hand to shift the narrative from a clash of personalities - which PM Modi has so far resoundingly won - to a debate about policies.
"You will see many changes and every change will be a reaffirmation of what the Congress's core beliefs are," said party MP and senior leader Jyotiraditya Scindia, who works closely with Rahul Gandhi.
"The right time has come to strike a chord with the masses against (Narendra) Modi's governance style, and we will not miss it," he said.
Congress insiders acknowledge their leader has sometimes made it easy for PM Modi's BJP to question his commitment to politics.
"The key problem with Rahul Gandhi has been his lack of consistency," said a senior party figure, who declined to be identified. "He frequently takes a break after few roadshows and it is this inconsistency that has been a huge issue."
But Congress leaders say Mr Gandhi has recently been finding his stride criticising PM Modi for failing to create jobs, while the party has won a handful of recent by-elections.
Mr Gandhi is traversing Gujarat, PM Modi's home state and where he was Chief Minister for 13 years, to fire up Congress workers who have not seen victory in state elections for two decades.
The Congress vice president has ditched some party rallies for one-on-one meetings with trade unions, dairy workers and small traders - a traditional powerbase of PM Modi that has been hit hard by recent economic reforms championed by the prime minister.
PM Modi has taken notice. Last week he told workers from his party that the Nehru-Gandhi dynasty would "destroy Gujarat".
BJP chief Amit Shah, who recently visited the Gandhi family bastion of Amethi in Uttar Pradesh, also Rahul Gandhi's parliamentary constituency, said this month that Mr Gandhi needs to swap his "Italian" glasses for "Gujarati" spectacles to see the economic development the BJP has brought to the region, in a jibe at his Italian-born mother's roots.
Rahul Gandhi, who rarely talks to the media, declined a Reuters interview request.
Rahul Gandhi's father, grandmother and great-grandfather were all prime ministers in post-independence India. But critics deride Mr Gandhi as a political lightweight who depends on his family name for power.
Bursts of political energy have been followed by lengthy absences. In 2015 he took nearly two months of leave, prompting PM Modi's party to accuse him of "holidaying" while parliament was in session.
The Congress now governs states home to less than 10 percent of the country's 1.3 billion population, its powerbase shrivelled under the onslaught of PM Modi's popularity.
Congress insiders acknowledge that the party is unlikely to win the December election in Gujarat, but cutting into the BJP majority in the state would send a powerful signal that the party under Mr Gandhi has a fighting chance against a still-popular PM Modi.
Rahul Gandhi has set up a new social media team in New Delhi to work on his image, and officials say he has been forging better ties with regional parties, often key powerbrokers in the country's politics.
On a recent tour of Gujarat, Mr Gandhi reached out to the frustrations of the state's powerful business community with the new national tax regime GST, including small traders such as those selling dry fruits. Different tax rates on almonds and cashews, imposed under the new tax launched by PM Modi's government in July, had left traders confused and damaged sales during the peak festival season.
"We have to show him as the face of the party before the Gujarat elections," said a close Rahul Gandhi aide who declined to be named.
BJP leaders say they are untroubled, and that any small bounce in Mr Gandhi's standing will die down once the economy strengthens. PM Modi has called the slowdown a blip.
"What does his claim to fame rest on?," said Nalin Kohli, BJP spokesperson, adding, "Two months of campaigning does not make him an active politician."
(By Tommy Wilkes and Rupam Jain. Writing by Tommy Wilkes; Editing by Sanjeev Miglani and Alex Richardson)