A poll of exit polls, an aggregate of 10 exit polls conducted in Gujarat, have predicted a clear majority for the BJP with 116 seats in the 182-seat assembly.
The party needs 92 seats to form the government. The Congress, according to this poll of exit polls, is expected to win around 65 seats, a slight improvement over its 2012 tally when it won 61 seats.
The assertion of Mr Rupani, who spoke before most exit polls had been announced, indicated that the exit polls had underestimated the BJP's performance.
The BJP has governed Gujarat for two decades. The campaign this year for the opposition has been led by Congress President Rahul Gandhi and has involved acrid attacks and counters.
The Congress' epic own-goal was its leader, Mani Shankar Aiyar, referring to the PM as "Neech" (lowlife), after which he was suspended from the party.
Gujarat election results will be announced today.