State Rep. Alex Sonson will run in the Democratic primary for state Senate next year against state Sen. Clarence Nishihara, D-18th (Waipahu, Crestview, Pearl City).

Sonson, an attorney who has served in the state House of Representatives since 2002, plans to make a formal announcement tonight at a fundraiser at the Disabled American Veterans hall near Ke'ehi Lagoon.

"At this time, I believe that I may be most effective as a public servant by using my experience and knowledge to serve a wider base of constituents as a state senator," said Sonson, D-35th (Waipahu, Crestview).

Nishihara, a retired public school vice principal elected in 2004, said he ran on a platform of honesty and integrity and believes he has put constituent interests ahead of his own. Nishihara had defeated fellow Democrat Cal Kawamoto, a veteran senator caught up in a campaign spending investigation, in the primary.

"I hope that my record speaks for itself," the senator said.

Sonson is chairman of the House Labor and Public Employment Committee and was involved in workers' compensation legislation last session. Nishihara is chairman of the Senate Tourism and Government Operations Committee and has also been active on education, public safety and judiciary issues.

The primary, since it pits two established Democrats, will likely be among the most competitive next year.

Reach Derrick DePledge at ddepledge@honoluluadvertiser.com.