The man who steered a mammoth programme to give a billion Indians an identity card is battling heavy odds in his bid to reinvent himself with his political foray as he faces a high-octane contest for the Bangalore South Lok Sabha seat in the April 17 polls.

Billionaire Infosys co-founder and face of UPA's marquee programme "Aadhar" Nandan Nilekani has turned what was initially perceived to be a "heavyweight versus newbie" fight into a hot contest too close to call.

Nilekani's opponent BJP's Ananth Kumar is a five-time MP who has his ears to the ground in the mostly middle and lower middle class dominated constituency that, barring in 1989, has been an inhospitable terrain to Congress since the late 1970s.

But the former IT honcho is no pushover, a fast learner that he is of the tricks of the trade, making the position not so cosy for a gregarious Kumar whose victory margins have been shrinking-- from 65,000 in 1999 to 37,000 in 2009.

In his different makeovers, 58-year old Nilekani, a Bombay IIT product, co-founded Infosys that became an icon of IT industry, was part of a task force on civic matters during S M Krishna's regime and headed UIDAI that brought him into public domain. Now, he has entered muddy waters of politics.

Bangalore South has eight assembly segments, with ruling Congress in the state and BJP holding four each.

True to its cosmopolitan nature, the constituency has considerable share of Brahmin, Vokkaliga and Muslim voters and a mix of upper and middle class voters. Both Kumar and Nilekani belong to Brahmin community.

"I am a unique candidate, not a unique identity candidate," Kumar says in a dig at Nilekani, who was the Chairman of the Unique Identification Authority of India (UIDAI) that oversaw "Aadhar" programme.

Nilekani has hit back and called Kumar "an absentee MP", alleging that he was not visible in his constituency, and promises the voters that he would be accessible to them.

The face that Nilekani presents, "Aadhar" has become a focal point for discourse in the constituency.

Dismissing Aadhar as "niraadhaar" (without a basis), Kumar has said it would be scrapped "lock, stock and barrel "if the NDA comes to power.

Kumar has asked only one question about Aadhar in Parliament, Nilekani has said, questioning his "sudden concern". He alleged that Kumar was "part of the pro-corruption, anti-development forces who are trying to discredit an anti-corruption effort."Nilekani enjoys a cult status among techies and the middle class but critics note that he is carrying the baggage of UPA rule.

Kumar, on other hand, is countering the anti-incumbency with the "Modi" card, that his party grassroot level workers expect will more than neutralise the negative factor.

Modi and Rahul Gandhi campaigned for their candidates in Bangalore.

The BJP prime ministerial candidate brought Nilekani in the line of fire, without naming him at a rally in Bangalore. "The Congress has named a person with thousands of crores of rupees as its candidate... but his project has resulted in thousands of crores of rupees going down the drain."

Nilekani has declared his and his wife's assets at over Rs 7,710 crore, making him the richest among the candidates who have filed their nominations so far.

In his campaign, Nilekani has blended both tradition and modern. He is using the social media to the hilt and his high tech campaign is also partly app-powered. Door-to-door canvassing, street corner meetings and greeting morning walkers in parks are also part of his strategy to reach out to voters.

Nilekani also has a support of a volunteer group called "Together With Nandan", which along with his wife Rohini Nilekani is playing crucial role in his campaign. They were recently joined by two eminent literary personalities and Jnanpith Awardees Girish Karnad and U R Ananthamurthy.

Kumar is helped by a well-oiled party machinery with committed cadres and is amply connected with the constituency. Kumar who speaks fluent Kannada scores big when compared to Nilekani, whose mother tongue is Konkani.

A total number of 23 candidates are in the fray.

JDS has fielded Human Rights activist Ruth Manorama and, making its foray into Karnataka politics, Aam Aadmi Party has fielded child rights activist Nina P Nayak.

Controversial chief of fringe right wing outfit Sri Ram Sene, Pramod Muthalik, who was discarded by BJP within hours of his admission into the party, is also in the fray from Bangalore South.

He has filed his nomination to challenge Kumar whom he blamed for his plight.