Kejriwal supporters in hundreds have been campaigning for him for days in Varanasi.
Vaibhav Maheshwari, who handles the media for the AAP in Uttar Pradesh, said, Kejriwal-Modi contest would not be symbolic. He said its outcome would be "stunning".
Kejriwal, who founded the AAP in November 2012, led the party to a dramatic debut in Delhi in December 2013 by winning 28 of the 70 seats, and then formed a minority government that lasted 49 days.
Here is the live reporting of Kejriwal's Varanasi visit: