With Swaraj failing to turn up at rallies scheduled in Keonjhar and Kendrapara, BJP's Odisha in-charge Arun Singh substituted her at the events.
Singh, accompanied by senior leader Bishnu Das, campaigned in Kendrapara.
"She could not come due to certain problems," a senior BJP leader said.
Meanwhile, Patnaik undertook extensive campaigning in Kendrapara and Jagatsinghpur Lok Sabha constituencies while voting was going on during the day at the Hinjili Assembly segment from where he is contesting, party sources said.
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He addressed rallies at Patkura, Kendrapara, Salipur and Aul under Kendrapara parliamentary constituency and Rahama, Jagatsinghpur, Tirtol and Paradip under Jagatsinghpur Lok Sabha seat.
Earlier, Patnaik had campaigned for BJD candidate Atanu S Nayak at Mahakalpada where BJP has fielded senior leader Bijay Mohapatra.
BJP's prime ministerial candidate Narendra Modi and Congress President Sonia Gandhi are scheduled to address meetings in the state tomorrow.