Airi is a senior leader of UKD, which had spearheaded the movement of statehood for Uttarkhand, and his support will strengthen Rawat's position on the seat.
Rawat is seeking his mandatory entry into the state Assembly as an MLA within six months of being sworn in as CM on February one.
Harish Dhami of congress had resigned from Dharchula to pave way for the CM to contest from that seat to become the member of the Assembly.
"Stability of the government will add a new dimension to the development of the state," Rawat's media in-charge Surendra Kumar quoted the chief minister as saying in his message.
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Thanking Airi for his support despite his party's affiliations, the chief minister said the senior UKD leader has gone beyond the limitations imposed by his outfit in the state's interest and termed it as a "rare gift to him in his political career".
"We will together grapple with the challenges ahead of us," Rawat said.