Profile: Manmohan Singh
Manmohan Singh, who has announced he will not remain India's PM after elections in 2014, is regarded by many as a man of great personal integrity, but whose term in office has been marred by a string of corruption scandals that have come to dog his administration.
After almost a decade in office, Mr Singh himself is still viewed as perhaps the cleanest politician in India, but many observers now say that is not enough to lead the country.
In ruling himself out for PM after the elections, Mr Singh singled out Rahul Gandhi - heir to India's Nehru-Gandhi political dynasty - as having "outstanding credentials", while berating the leader of the opposition Bharatiya Janata Party, Narendra Modi, as a "disastrous" candidate.
Widely regarded as the architect of India's economic reforms programme, Mr Singh, 81, is the first Sikh to hold the country's top post.
End Quote Manmohan Singh Prime Minister
My silence is better than thousands of answers”
He was first appointed in 2004 after the president of his Congress party, Sonia Gandhi, turned down the post, apparently to protect the party from damaging attacks over her Italian origin.
Then when Mr Singh guided Congress to a second, decisive election victory in 2009, he vowed that the party would "rise to the occasion".
But the gloss soon began to wear off and his second term has been in the news mostly for all the wrong reasons - several corruption scandals involving his cabinet ministers which allegedly cost the country billions of dollars, a parliament stalled by the opposition, and a huge policy paralysis that resulted in a serious economic downturn.
LK Advani, a senior BJP leader, has called Mr Singh India's "weakest prime minister".
Mr Singh has defended his record, saying his government had worked with "utmost commitment and dedication for the country and the welfare of its people".
And in an unusually combative mode, he recently said the BJP was indulging in divisive politics.
"I don't think that the party which indulges in politics that divides the country can bring development to the country," he told an election meeting.'Accidental PM'
A studious former academic and bureaucrat, he is known for being self-effacing and has always kept a low profile. His Twitter debut was noticed mostly for its dull entries and limited number of followers.
A man of few words, his calm demeanour had until recently won him many admirers.
Responding to questions on one scandal, over coal, he defended his silence on the issue by saying it was "better than thousands of answers".
Critics say there has never been any doubt that Sonia Gandhi is the real power centre in India and that Mr Singh has never been fully in charge.
Many also believe that he is just the safe, older figure, keeping the seat warm for the next generation of the Gandhi family.
The biggest triumph during his first five-year term was to bring India out of nuclear isolation by signing a landmark deal giving India access to American nuclear technology.
But the deal came at a price - the government's Communist allies withdrew support after protesting against it, and Congress had to make up the lost numbers by enlisting the support of another party amid charges of vote buying.Consensus builder
Mr Singh rose to political prominence as India's finance minister in 1991, taking over as the country was plunging into bankruptcy.
In his maiden speech he famously quoted Victor Hugo, saying that "no power on earth can stop an idea whose time has come".
That served as the launch for an ambitious and unprecedented economic reform programme.
The economy revived, industry picked up, inflation was checked and growth rates remained consistently high in the 1990s.
His unexpected appointment as finance minister capped a long and illustrious career as an academic and civil servant.
After attending Panjab University he took a master's degree at Cambridge University and a DPhil at Oxford.
But Manmohan Singh is a man acutely aware of his lack of political mass base. "It is nice to be a statesman, but in order to be a statesman in a democracy you first have to win elections," he once said.
He has never personally won a mass, popular vote, although he may claim the 2009 election serves as such. Rather, other leaders selected him.
When he tried to be elected to India's lower house, in 1999, he was defeated. He sits instead in the upper house, chosen by his own Congress.
Even so, he has enjoyed popular support, not least because he was seen as a clean politician.
A consensus builder, he has found himself presiding over a coalition of sometimes difficult, assertive and potentially unruly regional coalition allies and supporters.
And though he has earned respect for his integrity and intelligence, he also has a reputation for being soft and indecisive.
Some critics claimed that the pace of reform slowed and he failed to achieve the same momentum he had while finance minister.
As the first Sikh prime minister he made a public apology in parliament for the 1984 riots in which some 3,000 Sikhs were killed.China border
In his foreign policy, Mr Singh adopted the pragmatic politics pursued by his two predecessors.
He continued the peace process with Pakistan - though this process was hampered by attacks blamed on Pakistani militants, culminating in the Mumbai gun and bomb attack of November 2008.
He tried to end the border dispute with China, brokering a deal to reopen the Nathu La pass into Tibet which had been closed for more than 40 years.
Mr Singh increased financial support for Afghanistan and became the first Indian leader to visit the country for nearly 30 years.
He also angered many opposition politicians by appearing to end relationships with India's oldest ally, Iran.
History will remember him for bringing India out of economic and nuclear isolation, although some historians may suggest he should have retired earlier.