State Sen. Clayton Hee announced on Sunday that he will challenge Lt. Gov. Shan Tsutsui in the Democratic primary.

The senator made the announcement at Iolani Palace, flanked by his wife, Lynne Waters, former Gov. Ben Cayetano, Honolulu Prosecutor Keith Kaneshiro, and Princess Abigail Kawananakoa.

“I believe that now is the right time for me,” Hee said.

Hee told reporters that internal polls show him competitive against Tsutsui. Hee lost campaigns for lieutenant governor in 2002 and for Congress in 2006.

“You know, 10 years ago, I might have just done it just to do it,” the senator, 61, said. “Ten years later, at my age, we want to be sure we know how deep the pool is before we jump in.”

Hee is an old friend and political ally of Gov. Neil Abercrombie, who is facing state Sen. David Ige in the primary. Tsutsui, who as Senate president had formed a leadership alliance with Ige, has endorsed Abercrombie.

Hee said he would support whichever Democrat emerges from the primary. “That’s the horse that I ride,” he said. “That’s the way it’s supposed to be. We’re not supposed to pick and choose, but that’s just how it is.”

Hee also endorsed former Rep. Gil Riviere to replace him in his Windward and North Shore Senate District. Riviere switched parties last year and became a Democrat, intending to seek his former House seat, which he lost to Rep. Richard Fale in the Republican primary in 2012.

Fale has announced that he will run for Senate. Former Rep. Colleen Meyer, who lost a close campaign to Hee in 2012, will also run in the GOP primary.