Although the quintessential number two in the Congress-led government, the 76-year-old Mukherjee is a man of unparalleled experience who has the rare distinction of having served at different times as foreign, defence and finance ministers. He has presided over cabinet meetings when the prime minister has been away for the last 25 years, but somehow the top post has eluded him because of, what political observers widely feel, the wariness of the Gandhi family.

That wariness goes back to the time after Indira Gandhi's assassination in October 1984 when Mukherjee, a stickler for rules, is supposed to have pointed out to her son Rajiv Gandhi on a flight back from Kolkata that convention demanded that the second in command be the caretaker prime minister till the Congress party elected a new leader.

That was interpreted as a sign of his vaulting ambition and Mukherjee remained out of contention for the prime minister's job for the next 25 years.

A powerful orator and a formidable negotiator, Pranabda - as the Bengali 'bhadralok' is adoringly addressed - came to acquire in his five decades of parliamentary politics traits that have earned him the admiration of even his political foes. He is considered a walking encyclopaedia on virtually everything related to politics and governance that makes it difficult for any bureaucrat to hoodwink or trip him.

Remarked a former secretary in the government who worked under him when Mukherjee was foreign minister: "He has a photographic memory for the fine print and remembers negotiating details and their articles and clauses like nobody can. So whatever you tell him, he will tell you more about it."

His life journey began in December 1935 when he was born into a middle class family in Birbhum district of West Bengal. His father Kamada Kinkar Mukherjee was a Congress politician too, and politics came naturally to the young man.

After degrees in history, political science and law, Mukherjee gave up his two initial loves - teaching and journalism - to take to politics.

His parliamentary career began in 1969 when his home state, West Bengal, was in ferment, with the left-wing ultra, knowns as the Naxalites, on the rampage. He kept getting nominated to the Rajya Sabha until 2004 when he was elected to the Lok Sabha.

From the time he first became a minister for revenue and banking by Indira Gandhi in 1973, Mukherjee has held a variety of portfolios in successive governments. He first headed the finance ministry in 1982, and holds the same post today.

In between, Mukherjee went through a bad phase when, after the assassination of Indira Gandhi, he fell out of favour vis-à-vis Rajiv Gandhi. He remained out in the cold for a long time, during which he formed a Congress splinter group that died a quick death.

But once he returned to the government, particularly under Manmohan Singh, a man who was once his junior in the finance ministry, he emerged with his prodigious bank of knowledge and varied political experience as the principal troubleshooter and consensus-creator in the government.

He is the man the Congress - both Sonia Gandhi and Manmohan Singh - have turned to every time there is a political crisis. Each time, Mukherjee has risen to the occasion, and even if he has not always succeeded, he invariably left a mark in parliamentary debates.

His indispensability is reflected in the number of key ministerial decision-making groups, known as Group of Ministers, he has been asked to head since 2004 -- of the 183 groups formed, 83 were are under him.

All through his political career, he has been successful in maintaining an unblemished image and upholding probity in public life. He devours books, works well past midnight, and said in a rare peek into his personal life in an interview some years ago that he hardly was able to find time for his family and his only interaction was often limited to giving his wife a goodnight peck before retiring to bed well past the usual bedtime.

He is known never to have taken a holiday, except for his annual spiritual jaunt when he has a rendezvous with his favourite deity, Goddess Durga, at his ancestral home in Miriti village in Birbhum district, about 200 km from Kolkata. Adorning the pattabastra (robe) of a priest, Mukherjee religiously performs the rituals, reads from the 'Sree Sree Chandi' sacred text, and fasts during the three days of Durga Puja.

His sharp memory, quick wit and persuasive skills are widely respected. In what can be called a tribute, BJP star L.K. Advani once remarked that the Congress-led UPA government would not last a day but for Mukherjee.

His Congress colleagues whisper he is a Chanakya, ancient India's fabled political philosopher, but he largely well liked for his knowledge and sagacity.

"No one in the party is against him, he has no enemies," a Congress minister, who did not wish to be identified, told IANS.

He is down to earth, lives modestly, and has admitted many a time that he cannot speak polished English. For one who is supremely self-confident, he can be humble. But he has a temper, and has more than once apologized to MPs for raising his voice.

Once a pipe smoker, Mukherjee has now quit smoking. Today he tells people to kick the habit - by regularly hiking excise duty on tobacco.

He's not a movie buff, but his soft corner for the silver screen was amply evident when he, in his latest general budget, exempted films from service tax, saying they contributed immensely to national unity.

"I used to see some movies earlier. But recently I didn't have the luxury of having any time...except for one movie, watching which was I think, a part of my job. It was on air force...'Rang De Basanti'," he had famously said about the 2006 Aamir Khan-starrer.

Being a Bengali does not necessarily make Mukherjee a soccer fanatic. During his tenure as India's defence minister, soccer clubs of Kolkata petitioned him to let them build permanent infrastructure over the football grounds, which are on army-owned land, but to no avail.

Mukherjee, a devoted family man, is married to Surva Mukherjee. The couple have two sons and a daughter. Surva is a singer of repute and her troupe performs Rabindra Sangeet.

His oldest son Abhijit Mukherjee, following his father's footsteps, has joined politics and is now a member of the West Bengal legislative assembly.