Rupani was elected the leader of the BJP legislature party in Gujarat, Union minister Arun Jaitley said.
Deputy Chief Minister Nitin Patel will continue to be the second in command, after he was declared the deputy leader of the legislature party by Jaitley, the central observer appointed by the BJP leadership for the election.
Rupani was an acceptable face in the party and the BJP did well in the just ended Assembly elections in his home district.
BJP president Amit Shah had said during the campaign that the party was fighting the election under Rupani and Nitin Patel.
Rupani's proximity to the top party leadership, his clean and caste neutral image apparently tilted the scales in his favour.
Jaitley said the central observers, including BJP general secretary Saroj Pandey, asked the MLAs for names for the post of the leader and deputy leader of the legislature party, and one of them--Bhupendra Sinh Chudasama-- suggested Rupani and Patel for the posts. Five others backed Chudasama's proposal.
The Union minister said he asked the MLAs to come up with more names for the two top posts, but as nobody came forward, Rupani and Patel were declared elected as the leader and deputy leader of the legislature party.
Asked why was there the suspense over who would be the next chief minister, Jaitley said, it was a media creation. He said Rupani will hold consultations with elected MLAs before forming the new government. Rupani, he said, will meet Governor O P Kohli and finalise the date for the swearing-in.
There were grievances against Rupani and Patel, with the BJP seat tally not touching even 100 -- compared to BJP President Amit Shah's repeated claims that it will win 150 seats. But all those grievances were put to rest after BJP announced that the two leaders will continue to hold the top posts in Gujarat.
Earlier, Rupani had said the party's parliamentary board will take the final decision.
December 25 is the likely date for the swearing-in of the new ministry as it is the birthday of former prime minister and BJP stalwart Atal Bihari Vajpayee, PTI sources said.
(With PTI inputs)