NEW DELHI (AFP) - India's Prime Minister Narendra Modi faces the first real test of his popularity on Saturday when voters in Delhi elect a new state government, with a self-styled anarchist bidding to stall the premier's bandwagon.

The results, to be announced on Tuesday, could also prove to be a new low for the long-ruling Congress party, which suffered a landslide defeat to Mr Modi's Bharatiya Janata Party (BJP) in May's general election.

Since May, Mr Modi has been the master of all he surveyed as his Hindu nationalist party romped to victory in a string of state elections. But Delhi, which the BJP surprisingly failed to win in December 2013, could prove elusive once more and deliver the first real reverse for the Premier who has been enjoying an extended honeymoon with voters.

Standing in his way is a familiar foe: Mr Arvind Kejriwal who quit after a chaotic 49-day reign as Delhi chief minister but whom opinion polls say could return to power.

Mr Kejriwal, leader of the anti-corruption Aam Aadmi Party, failed to prevent Mr Modi from winning the parliamentary seat of Varanasi in May.

But he could deliver fresh embarrassment to the Indian PM who has rolled out his big guns to prevent the former taxman from returning to power.

Mr Modi put his two top lieutenants - BJP president Amit Shah and Finance Minister Arun Jaitley - in charge of the campaign while a former top policewoman Kiran Bedi was handpicked as the choice for chief minister.

Ms Bedi's selection has opened a can of worms, with many BJP activists furious at having to campaign for the 65-year-old who has a history of disparaging the BJP.

A former reality TV show host, Ms Bedi is a seasoned media performer. But Mr Kejriwal has proved his pulling power among working class and minority voters, with even impromptu appearances drawing thousands.

The 46-year-old, who has been dubbed 'Mufflerman' after spending much of the campaign swaddled in scarves, has frequently apologised for quitting and leaving the city without an elected government for nearly a year.

Mr Kejriwal famously declared himself an anarchist during his brief tenure and staged several protests outside government offices.

This time round he has tried to cut a more sombre figure, insisting he can be relied on to form a stable government to guarantee cheap utility bills and deliver on pledges such as free Wi-Fi.

But his main selling point remains as the underdog taking on the establishment - not unlike Modi's own pitch last year.

"My fight is your fight. Who am I? An ordinary man fighting all your battles," Mr Kejriwal said at a rally in northwest Delhi last week.

Rattled by Mr Kejriwal's popularity, Mr Modi himself has taken to the campaign trail, portraying his rival as a "backstabber" who betrayed voters last time round by quitting so early.

Speaking to AFP during a roadshow in east Delhi, Ms Bedi also tried to dismiss Mr Kejriwal as a publicity junkie.

"People are now fed up of this drama, spectacle. They don't want it any more," she said.

"They want stability, serious governance and progress, which only we can give."

Mr Manoj Joshi, of Delhi's Observer Research Foundation think-tank, said the contest was too close to call, but said a defeat for the BJP would be a serious blow to Modi given how much he invested in the campaign.

"Modi has been on a winning streak for the past one year. A loss here will break its momentum and re-enthuse the opposition ranks," he said.

"An opposition government here will create problems because Kejriwal and his party are opposed to foreign direct investment in retail, the land acquisition bill and several other key reforms planned by this government."

A senior Delhi BJP leader, speaking anonymously, acknowledged the verdict of the 13-million strong electorate would have a wider significance.

"It may only seem like a small municipality in terms of area and population... but every state government always gets much more publicity and media attention than anywhere else," he said.

A strong performance for Mr Kejriwal and Aam Aadmi - which only won four parliamentary seats at national polls - would breathe new life into a party whose original anti-corruption message has taken a back seat in the campaign.

Mr Kejriwal began his term in a blaze of glory, taking the metro to his inauguration and initially shunning his official residence.

But his government was soon mired in scandal, with a raid on a largely African neighbourhood sparking racism claims.

His decision to quit was widely attributed to his desire to challenge Mr Modi on the national stage, fuelling accusations of over-ambition.

While Mr Kejriwal could get another chance to prove himself, Congress - which ruled the capital for 15 years - can only look on in despair with the party tipped to come a distant third.