What formalised the split in the Congress in late 1960s?

The correct answer is Option (1) → The defeat of the official Congress candidate in the Presidential elections.

Option (1) The defeat of the official Congress candidate in the Presidential elections. — Correct. In the Presidential election of 1969 V.V. Giri won and the official candidate, Sanjeeva Reddy, lost: the defeat of the official Congress candidate formalised the split in the party.

Option (2) Indira Gandhi’s bold strategy and initiatives to give the government policy a Left orientation in 1967. — Incorrect. Her Left initiatives, such as the Ten Point Programme of May 1967, turned the power struggle with the Syndicate into an ideological one. They sharpened the rivalry, but the split itself was formalised only after the Presidential election of 1969.

Option (3) The challenge of political succession after the death of Lal Bahadur Shastri. — Incorrect. After Shastri’s death in 1966 Indira Gandhi was chosen as Prime Minister. This succession began her rivalry with the senior leaders, but it did not divide the party.

Option (4) The ruthless abuse of power during the Emergency period. — Incorrect. The Emergency was declared in 1975, years after the Congress had split in 1969.