Emulating Indian independence hero Mahatma Gandhi, Rahul Gandhi was set Wednesday to begin a "long march" seeking to halt the seemingly inexorable slow decline of his once-mighty Congress party.

The Grand Old Party, which governed for decades after India's 1947 independence from Britain, is a shadow of its former self, discredited and crushed under the electoral juggernaut of Prime Minister Narendra Modi's Hindu nationalist Bharatiya Janata Party (BJP).

The BJP thrashed Congress at the last two elections, with Modi deriding Gandhi -- descended not from the Mahatma but from India's first prime minister Jawaharlal Nehru -- as an out-of-touch pampered princeling and playboy.

Before setting off on the trek Gandhi prayed at a monument in Sriperumbudur in the southern state of Tamil Nadu where in 1991 his father Rajiv Gandhi was assassinated -- like his grandmother Indira seven years earlier.

"I lost my father to the politics of hate and division. I will not lose my beloved country to it too," Gandhi, 52, said on Twitter.

He then headed to the southernmost tip of India, before traversing the nation, covering 3,500 kilometres (2,175 miles) across 150 days and ending in Kashmir -- although it was unclear if he will actually walk all the way.

The aim, he said, is to highlight rampant unemployment, soaring inflation and growing polarisation between majority Hindus and religious minorities like Muslims under Modi, 71.

"I want to ask you whether price rises or hatred strengthens the country... Narendra Modi and the BJP are weakening the country," Rahul told a rally in New Delhi on Sunday ahead of the mega march.

"The Congress party, on the other hand, unites the country. We erase hatred and when hatred is erased, the country moves faster."

Mahatma Gandhi famously trekked some 380 kilometres (240 miles) in 1930 to protest a salt tariff imposed by British rulers, in a seminal moment in the independence struggle.

But Rahul, dubbed an "empty suit" in leaked 2005 US diplomatic cables, is seen as a reluctant leader despite being the great-grandson, grandson and son of three past premiers of the world's biggest democracy.

Gandhi quit as party president after the 2019 election debacle and was replaced on an interim basis by his mother Sonia Gandhi, 75, widow of Rajiv.

If he returns as president, which remains unclear, he faces a huge battle to revive the party, in power in just two out of 28 states and in coalition in four others.

Analysts say Congress lacks Modi's common touch and is missing a counter-narrative to the BJP's politics which is infused with a heavy dose of "Hindutva" -- an ideology that believes in making India an exclusive Hindu state.

The march "is not a gimmick. Rahul Gandhi sincerely believes in religious harmony. But the people are not interested. So, it will fail," said political analyst Parsa Venkateshwar Rao Junior.

"Rahul and Congress would have to work hard on the ground, find out the problems people are facing in different parts of the country," he told AFP.

"(The people) need someone to voice their dissatisfaction."