As he contemplated the vast crowds that greeted Narendra Modi in India's holiest city, the would-be prime minister's top aide proclaimed the wave of support for his boss had become a "tsunami".

Rather than deny the opposition's assertion, the governing Congress party shot back that tsunamis leave a trail of death and destruction.

The salvo was typical of the war of words being waged in Varanasi, one of the final contests in the world's biggest election and whose combatants include two of India's most talked-about politicians.

If his Bharatiya Janata Party's plan comes off, Modi will emerge next week as Varanasi's member of parliament and India's prime minister.

But opposing him is anti-corruption champion Arvind Kejriwal, who six months ago prevented the BJP from taking charge of Delhi's state assembly in a stunning electoral debut.

The expectation this time is of a win for Modi in Monday's poll, the last day of voting in the whole six-week election. National results are due next Friday.

"Everyone in Varanasi, everyone in India, knows that Modi is the frontrunner," said T. P. Singh, a politics professor at the city's Banaras Hindu University.

"The people of Varanasi are excited that they won't just be voting for their MP but also for their PM."

A sacred city around 420 miles (680 kilometres) east of Delhi, Varanasi is a perfect platform for Modi to present himself as a sound administrator and proud Hindu.

The city on the banks of the river Ganges teems with temples and traffic, and it is regarded as particularly auspicious for Hindus to be cremated by the holy waters. Boys play cricket only yards from the burning bodies.

- Higher calling -

"It doesn't so much feel like the BJP has sent me here but rather that Mother Ganga has summoned me," said the 63-year-old Modi, who elbowed a sitting BJP veteran aside in order to stand.

More than 100,000 people lined the streets as Modi crawled through on an open-top truck, prompting top aide Amit Shah to forecast a "tsunami... that will wipe out" his rivals.

Modi's pitch has been to revive a city whose famous silk industry is fighting for survival. A BJP "vision document" includes pledges to clean up the filthy Ganges and make Varanasi an education hub.

The BJP's national secretary, Rameshwar Chaurasia, says Modi's candidacy should also have a knock-on effect in neighbouring states.

"Democracy is a game of numbers and it was felt Modiji (ji is an Indian honorific) would change the dynamics of at least 59 seats," he told AFP.

Uttar Pradesh state, which is home to Varanasi, accounts for 80 out of 543 seats in the parliament, making it by far the most important state.

Congress appears to be an also-ran in Varanasi after fielding a former BJP cadre who is accused of attempted murder.

Laxman Nishad, who rows pilgrims down the Ganges, said he would vote for Modi, a four-term chief minister of the relatively thriving coastal state of Gujarat.

"He has turned Gujarat into a golden place," said the boatman, 65.

If Modi's governance record adds to his appeal, his reputation as an unabashed Hindu nationalist as a former member of the radical Rashtriya Swayamsevak Sangh group divides voters.

"He's a hard worker and capable man who believes in Hindu culture," said Swamy Shesh Naryan as he took an early morning dip in the river. "There is nothing wrong with someone who is proud of his roots."

But Taj Muhammad, a Muslim lawyer in Varanasi, said: "We don't think that even one percent of (Muslim) votes will go to him."

The 63-year-old leader remains deeply controversial after more than 1,000 people, mainly Muslims, were killed in riots in Gujarat in 2002 shortly after he came to power.

- Grassroots competition -

While his campaign events have been dwarfed by Modi's, Kejriwal has drawn support from Muslims, who account for around 13 percent of Varanasi's population.

Named along with Modi as one of Time magazine's 100 Most Influential People, Kejriwal has been telling voters that all parties have been guilty of fostering corruption in Varanasi.

"This is not my fight, it's everyone's fight who wants India to be free of corruption, who wants decent roads in Varanasi, who wants to see poverty eradicated from this country," he said at one rally.

Kejriwal caused shockwaves in December when a strong showing by his Aam Aadmi (Common Man) Party in state elections allowed him to become Delhi chief minister before quitting after 49 days, stalling his party's momentum.

There are few signs of a similar upset this time.

While posters of Kejriwal and his trademark broom are a common sight on Delhi rickshaw cabs, those in Varanasi are mainly adorned with Modi's beaming image.