In an interview to India-West news which was published on Monday, Varghese, who served in the White House with Biden and former President Barack Obama, said: "Biden is the only candidate who can get us through the Trump era.
"People are looking for a moral character to leadership. Biden's character is exactly what we need... He is a trusted figure."
Biden, who has led the crowded field since he entered the 2020 race last April, is hugely popular with Indian-Americans, who have given him the bulk of their donations in the third quarter of 2019: about $246,000; and $128,000 in the second quarter.
Biden has also earned some key endorsements, including from the American Association of Physic of Indian Origin (AAPI) Victory Fund, and California Representative Ami Bera.
Varghese told India-West that Biden will win the Democratic nomination "as long as he continues to be his authentic self".
About Biden often speaking of his eldest son Beau, who died in 2015 of an aggressive form of brain tumour, during campaign trails, Varghese said the candidate's sharing of the loss of his son resonates with people.
Varghese's national political career began two decades ago with former Vice President Al Gore's bid for the White House.
He moved to the White House in 2010, serving in various capacities, most notably as the Assistant to the President for Management and Administration, a role in which he managed the day to day operations of the White House, including budget and personnel.
According to the latest RealClearPolitics national Democratic primary polling average, Biden was leading the Democrat race with 27.2 per cent, followed by Senators Bernie Sanders and Elizabeth Warren with 23.5 per cent and 15 per cent, respectively.
( With inputs from IANS )