The sudden announcement that Sonia Gandhi, the president of India's ruling Congress party and head of the Nehru-Gandhi dynasty, had left for America to undergo an operation has highlighted the extraordinary powers she enjoys and brought to the fore the question of her successor.
Sonia Gandhi shuns the limelight, but still holds great influence in India
Hardened members of parliament in Delhi wept when, after leading the Congress party to a surprise victory in the 2004 general election, Sonia Gandhi announced that she would not become prime minister.
Those tearful MPs need not have worried: Sonia was not about to go away, to leave them leaderless.
And now every member of the ruling party, from the top down, is worried about whether Sonia will recover to continue leading them, and if not, how she will manage the succession.
When Sonia gave up the chance to become prime minister, she made it clear that she would still be the boss by choosing Dr Manmohan Singh to do the job.
He is renowned for his honesty and his knowledge of economics, but has spent most of his life as a bureaucrat and politically he is entirely dependent on Sonia.
Sonia remained President of the Congress party. It is a position without any constitutional authority but she has ensured it makes her more powerful than the prime minister.
In the shadows
Sonia Gandhi's power derives from being the head of the Nehru-Gandhi dynasty which has dominated Indian politics since the time of Jawaharlal Nehru, the first prime minister after India gained its independence.
Italian by birth, she became a member of the family by marrying the imperious Indira Gandhi's eldest son Rajiv.
Manmohan Singh has had to find the funds to pay for Sonia Gandhi's policies
Sonia never showed any interest in politics and did not want her husband to go into the family business. So long as he was prime minister, she remained in the background.
For six years after Rajiv's assassination, there was no member of the dynasty in the government or the party, but Sonia refused to fill the vacuum.
It was not until 1997, after the Congress had lost a general election and was falling apart, that Sonia stepped in to hold the party together.
The Congress party has unshakeable faith in the Nehru-Gandhi dynasty, but Sonia also owes her immunity from criticism to doing the opposite of what a politician usually does - she avoids the limelight and shuns publicity.
By refusing to become the prime minister, she has left Manmohan Singh to face all the flak that office attracts.
She very rarely gives interviews, she says very little in parliament and she does not intervene publicly when the government faces crises. But Sonia does appeal to the public over the heads of parliament and the press by addressing rallies.
Once again, Sonia Gandhi has shown that, unlike most politicians in democracies, she does not feel obliged to explain herself
At her rallies, Sonia always puts across the message she learnt from her mother-in-law - the message which says: "I am on the side of the poor".
In order to demonstrate whose side she was on, Indira passed a number of radical socialist measures with unfortunate consequences for the economy.
Sonia has demonstrated her option for the poor by forcing Dr Manmohan Singh to establish schemes to guarantee work for unemployed villagers and subsidised food for a sizeable proportion of the population.
The prime minister has to find the money to pay for Sonia's pro-poor policies. But he is a cautious economist, and someone who has worked closely with him told me one of his favourite maxims is "money does not grow on trees". Yet he still has to find the funds for the pro-poor schemes because Sonia has told him to.
Secrecy and succession
Typically, there was no government announcement about Sonia's departure for America. The Congress party issued a bald statement bereft of any information about her illness or the hospital where she was being treated.
This was justified on the grounds that her health was a personal matter and the people of India were asked to respect her family's request for privacy.
Rahul Gandhi (r) is next in line to succeed his mother
But India's two leading business papers did not agree to that request. One of them, the Economic Times, said the secrecy was reminiscent of the days of the Iron Curtain when "doddering old leaders of ruling Communist parties ailed, were hospitalised and died, and their countrymen were kept in the dark".
Once again, Sonia Gandhi has shown that, unlike most politicians in democracies, she does not feel obliged to explain herself.
What is more, she has demonstrated that she alone will nominate her successor, and when the time comes, he will be her 41-year-old son Rahul.
The Congress party has issued a statement saying that, while Sonia is in America, its affairs will be run by a quartet consisting of Rahul and three others whose only obvious qualities are their utter loyalty to his mother.
But there is one question which remains to be answered.
When the time comes for Rahul to succeed, will Sonia hand the party to him so that he can continue to exercise his authority in the way she has done, or will she feel that he should become prime minister?
In which case, he will have to explain himself and take responsibility for his decisions.
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