Sources within the YSR Congress stated that their leader Jagan has decided to back Pranab rather than BJP's nominee PA Sangma. They also added that this decision comes since Jagan was acknowledging the large number of Muslims who voted for the YSR Congress in the recent bypolls that the party won by a sweeping margin. He also wanted to maintain the secular stance of the party.
Jagan had, in earlier instances, stated that he would support either the UPA or a Third Front in the 2014 elections and that he would never back the BJP-led NDA.
The other reason on the YSR Congress' support to Pranab is that the Congress veteran might become the President with or without the party's support. With the added fact that the President's post is essentially non-political in nature and that supporting it will only add to the party's secular credentials.