Mr Reddy was one of the most influential politicians of the ruling party
YS Rajasekhara Reddy was an Indian politician who could boast a formidable mass following.
He rose above the bitter factionalism that enfeebled his Congress party in southern Andhra Pradesh state and became a figure largely accepted by all sectors of the party.
He had a reputation for social welfare schemes, which were often derided by his critics as "populist".
Mr Reddy and his Congress government have won the last two state elections in a row.
Andhra Pradesh is one of India's largest and most important states - but also one of extremes.
Rich, feudal landlords and business oligarchs abound as well as farmers who live in dire poverty. As crops have failed over successive harvests, many farmers in Andhra Pradesh have committed suicide after failing to pay off their debts.
The state also faces a separatist movement in the poverty-stricken Telangana region and a Maoist insurgency which appears to be on the wane.
Mr Reddy's death in a helicopter crash in his native Andhra Pradesh state has left the state without a prominent champion of social welfare schemes.
A trained paediatrician and a devout Christian, Mr Reddy's rise in politics coincided with the emergence of India's murdered former PM Rajiv Gandhi in the Congress party.
"Rajiv Gandhi spotted me. Since then I never looked back," Mr Reddy said once.
He was elected four times to parliament and five times to the state assembly.
In 2003, he embarked on a low profile journey on foot across his state and defied political pundits with his surprise win in state elections the following year over rival N Chandrababu Naidu, the pro-reform chief minister and leader of the regional Telugu Desam Party.
Once in power, Mr Reddy jettisoned his predecessor's reformist policies and worked hard to implement many popular social welfare schemes including a massive irrigation expansion scheme, old age pensions, and a successful jobs-for-work programme for villagers.
Mr Reddy was well known for his social welfare policies
Mr Reddy and his government were voted back to power in the state elections this year.
YSR, as he was popularly known, brought back "social democratic politics and schemes" to Andhra Pradesh after five years of controversial economic reforms by his predecessor.
The Congress party has appointed his low-profile finance minister K Rosaiah as his successor, but finding a permanent replacement will be difficult.
"YSR's death is a massive setback for the Congress party. It is always difficult to replace a leader with a mass base. It is not going to be easy and it will take a lot of time," says political scientist Jyotirmaya Sharma.