State Sen. Clayton Hee is expected to announce on Sunday that he will challenge Lt. Gov. Shan Tsutsui in the Democratic primary.

Hee’s late entry into the primary poses danger for Tsutsui, who is still unknown to many voters. The move could also unsettle Gov. Neil Abercrombie, a friend and ally of Hee’s, who has his own primary race against state Sen. David Ige but will likely feel obligated to help Tsutsui.

Hee has had a productive legislative year to use as his springboard. The chairman of the Senate Judiciary and Labor Committee had a hand in the historic passage of a marriage equality law last fall, pushed to increase the minimum wage to $10.10 an hour by January 2018, and had a role in the deal to preserve 665 acres at Turtle Bay Resort from future development.

Hee also helped shepherd Michael Wilson, Abercrombie’s third appointment to the state Supreme Court, through a contentious, and at times ugly, Senate confirmation after the Hawaii State Bar Association rated the circuit judge unqualified.

"For me, it’s an opportunity to work in the administration," Hee, 61, said in an interview. "I’ve spent a lot of time at the legislative level. It’s been a terrific privilege. We’ve done a lot of good things, in my opinion, with justice and equality, minimum wage, the conservation easement at Turtle Bay, animal welfare legislation, shark-finning legislation.

"And so for me, at this time in my career, this is an opportunity to see if I can meet the next challenge."

Hee, who has scheduled an announcement Sunday morning at Iolani Palace, can use money from his Senate campaign account for a lieutenant governor’s bid. The senator had raised $518,000 and had about $460,650 in cash on hand at the end of December, money he stockpiled over the past few years.

Tsutsui had brought in $425,000 through December and had about $357,000 in cash on hand.

A Hawaii Poll taken in February found that 20 percent of those interviewed had a favorable view of Tsutsui, while 71 percent had not heard of the lieutenant governor or did not know enough about him to form an opinion.

Tsutsui, 42, a former state Senate president, ascended to the state’s No. 2 post in December 2012 when Abercrombie appointed then-Lt. Gov. Brian Schatz to replace the late U.S. Sen. Daniel Inouye.

The lieutenant governor has split his time on Maui, where he lives, and Oahu, and has focused his policy work on developing after-school programs for middle-school students.

Tsutsui, first elected to the Senate in 2002, was the youngest Senate president. He also served as the vice chairman of the Senate Ways and Means Committee. Likable and outgoing, he has earned the loyalty of many former colleagues and Senate aides.

"I am humbled by the support I’ve received from the people of Hawaii and I look forward to a spirited campaign that will allow us to take our message to the voters," Tsutsui said in a statement. "In the meantime, there is much work to do as Lt. Governor and I will continue to work hard to meet the needs of Hawaii’s people."

Abercrombie reiterated his support for Tsutsui. "Since accepting the appointment as Lt. Governor, Shan Tsutsui has been a solid partner in my administration’s policies and initiatives. From the time he assumed office in December 2012, I expressed my support for his election efforts for Lt. Governor," the governor said in a statement.

"Sen. Clayton Hee has been a longtime friend, both personally and politically. Hee’s entrance in the race will result in a spirited contest that shows the strength and diversity of the Democratic Party."

Elwin Ahu, a former state judge and senior pastor at New Hope Metro, is the leading Republican candidate for lieutenant governor.

Hee has at times been a disruptive force in the Senate’s factional politics.

The senator has interrogated judicial nominees and Cabinet appointees to a degree some of his colleagues thought crossed the line. He has also had confrontations with fellow senators, on the Senate floor and in private, where he was perceived as brusque and overbearing.

Then-Senate President Colleen Hanabusa replaced Hee as Judiciary chairman in 2007, but he reclaimed the post — and took over a large fourth-floor office suite — after Hanabusa left for Congress and Tsutsui became Senate president in 2010.

Partial to sunglasses and cowboy boots, Hee is as adept as anyone at the Capitol at the tactical nuances of legislating, and has prevailed even when he appears isolated, as this year’s negotiations on the minimum wage proved.

"Let’s put it this way," he said. "I would be the first to share with anybody about engaging in things that I wish I could have a do-over. I’ve made mistakes. There’s no question about that. And those mistakes I own. They belong to me."

But he said he believes his approach has gotten better over the years and that "things can get done if you pursue it hard enough and with vigor and, hopefully, with a little more diplomacy than I may have had in the past."

The rancher and former educator, elected to the Senate in 2004, is in his second stint as a senator, after serving from 1984 to 1988. He also represented Molokai, Lanai and West Maui in the state House from 1982 to 1984. He was a trustee for the state Office of Hawaiian Affairs from 1990 to 2002, some of the agency’s most tumultuous years.

Hee ran unsuccessfully for lieutenant governor in 2002 and for Congress in 2006.

Hee said he would use the lieutenant governor’s office, which does not always have the highest profile, as a voice for animal welfare, climate resiliency and Native Hawaiian issues, topics often left off of or at the back end of a governor’s agenda.

"My own experience is the office is what you make of it," he said.

After Hee’s Windward Senate district was redrawn after the Census to include all of the North Shore, he had a tight re-election campaign in 2012, defeating former Rep. Colleen Meyer, a conservative Republican, by less than 1,000 votes.

Rep. Richard Fale (R, Waialua-Kahuku-Waiahole), a Mormon who opposes gay marriage, has announced that he will run in the Republican primary in Hee’s district, hoping to tap into the disappointment in the Mormon-dominated Laie region about the special session last year. Meyer also plans to run in the GOP primary.