Tim Johns, an executive at the Hawaii Medical Service Association and a former director of the state Department of Land and Natural Resources, said Friday that he will chair U.S. Rep. Mazie Hirono’s Democratic primary campaign for U.S. Senate.

Johns was DLNR director when Hirono was lieutenant governor for Gov. Ben Cayetano.

“Coming from my longtime support, and knowing her values and knowing her personally, I just felt like it was really important for all of us to be thinking about the future of Hawaii,” he said of his decision to volunteer on the campaign. “It’s a very important race, and I think it was very important for me to jump in and do what I can to help Mazie be successful in this way.”

Betsy Lin, Hirono’s chief of staff in Washington, D.C., has taken a leave of absence to work on the Senate campaign. Lin helped with U.S. Sen. Daniel Akaka’s successful primary campaign against former U.S. Rep. Ed Case in 2006.

Hirono and Case are competing in the primary to replace Akaka, D-Hawaii, who is not seeking another term.

Case has Lloyd Nekoba, a trusted former adviser to Cayetano and Gov. Neil Abercrombie, to manage his campaign.

Former Gov. Linda Lingle, the leading Republican contender, has turned to retired Maj. Gen. Robert G.F. Lee as her campaign manager.