Solution

The formal split in Congress took place in 1969 on the issue of nomination of the candidate during presidential elections:
1. Despite, Indira Gandhi’s reservations, the Syndicate nominated Neelam Sanjeeva Reddy, as the official Congress candidate for ensuing Presidential elections.

2. Indira Gandhi retaliated the situation by encouraging Mr. V.V. Giri, the then Vice-President, to be nominated as an independent candidate.

3. During election, the then Congress President S. Nijalingappa issued a whip asking all Congress MPs. MLAs to vote for N. Sanjeeva Reddy.

4. On the other hand, after silently supporting V.V. Giri, the Prime Minister Mrs Indira Gandhi openly called for a conscience vote to vote the way they want.

5. Elections went in favour of V.V. Giri due to this diplomatic effort and N. Sanjeeva Reddy was defeated.

6. The defeat of N. Sanjeeva Reddy, the formal Congress candidate, formalised the split of party into two:
(a) Congress (O), i.e. organisation led by syndicate, known as Old Congress.
(b) Congress (R) i.e. requisitionists led by Indira Gandhi, known as New Congress.