Priyanka Gandhi Vadra, daughter of Congress president Sonia Gandhi, said the AAP was an important opponent in Saturday's assembly polls in Delhi.
"I think it's definitely an important opponent in this election," Priyanka told reporters after casting her ballot.
Her husband Robert Vadra was with her.
She also hoped that Congress would overcome difficult times.
"Congress has faced difficulties before and it has always come through, I am sure it will come through," she said.