"We are fully confident that Pranab Mukherjee would do justice as the Constitutional head, first citizen of the country," YSR Congress Lok Sabha member M Rajamohan Reddy said.
The party has decided to support Ansari, who belongs to Muslim minority community, he said.
Asked about YSR Congress's allegation that a conspiracy has been hatched against Jagan by the Congress leadership, Rajamohan Reddy said, "They are valid points. We have two options. We have taken this decision."
Asked if the party has set aside its allegations for the Presidential election, he said, "It is not like that. We had to take a decision for election of President of India and we have taken this decision. This has nothing to do with other things."
Replying to a query, he said the "Congress leaders claim that they have nothing to do" with the cases involving Jagan and that "it is all happening as per court's directions."
The YSR Congress had earlier said Mukherjee called up its honorary president Y S Vijaya Lakshmi and sought the party's support for his candidature.
Opposition-backed P A Sangma had met Vijaya Lakshmi and other YSR Congress leaders here to seek party's support to his presidential bid.
YSR Congress has 17 MLAs in the Andhra Pradesh Assembly and two Lok Sabha members, including Jagan.