(CNN) A top California Republican says he's not planning on running for the California Senate seat up for grabs in 2016 following the retirement of Barbara Boxer.

Neel Kashkari, the man who won that state's GOP nomination for governor, and a presumed Republican frontrunner for the 2016 vacancy, has decided to stay on the sidelines.

Aaron McLear, an adviser to Kashkari, told CNN Friday evening the 2014 Republican gubernatorial nominee will not make a bid for the open Senate seat.

While he lost handily to Gov. Jerry Brown in November, Kashkari, 41, a son of Indian immigrants, helped work towards redefining a stagnant California Republican Party that had been roundly dismissed as overly rich and overly white by the state's voters.

Read More