Krishna Tirath, a union minister in the United Progressive Alliance (UPA) government, is the Congress's candidate from Patel Nagar. The leader had rejoined the Congress last year after being a BJP member since 2015.
A year after the Congress's drubbing in the 2014 national election, Ms Tirath, the party's prominent face in the national capital, had joined the BJP.
"There has been a change in the thought of the Congress. Traditions have ended," she had told NDTV, adding, "the people below have changed the atmosphere. There is no hearing for complaints even in cases of "harassment."
The Congress had said Krishna Tirath was upset at not being given a party ticket.
Mr Tirath had contested the 2015 Delhi Assembly polls on BJP ticket but lost to the Aam Aadmi Party. She has been a two-time MP from Delhi.
Ms Tirath had been a Congress legislator and an MP from Delhi and served as a Union minister of state with independent charge for women and child development in the Manmohan Singh government.
She had contested the national elections from Delhi in 2014 and lost to the BJP's Udit Raj.
The exit polls for the Delhi Assembly election have predicted a massive win for the Aam Aadmi Party.
Arvind Kejriwal's Aam Aadmi Party (AAP) is set for a hat-trick in Delhi with around 56 of 70 assembly seats, predicted NDTV's poll of exit polls after voting in the capital on Saturday. An aggregate of five exit polls also said the BJP will win 14 seats and the Congress, zero.
The Congress, however, is hoping for a turnaround.
"Let others celebrate the exit poll results. I am confident that the results on February 11 will startle everyone," chief spokesperson of Delhi Congress Mukesh Sharma was quoted as saying by news agency PTI.