Mwaita was a long-serving civil servant, rising from a junior officer to the position of Commissioner of Lands (2000-2003). As the Commissioner of lands, he was instrumental in the degazettment of in Mau forest land to pave way for the issuance of title deeds to Ogiek squatters.
Mwaita is the incumbent MP for Baringo Central since December 2007. He was first elected in the Kenyan parliamentary election, 2007 in December 2007, winning the seat for Baringo Central Constituency and defeating the incumbent Gideon Moi (the son of former President Daniel arap Moi). He ran on an ODM ticket and managed to garner 26,603 votes compared to Gideon Moi's 7,527.