At least 16 races for the Oregon House and Senate in 2020 will not feature an elected incumbent, suggesting there may some highly contested partisan contests and will be significant turnover in senior leadership.

One cause for the turnover: An open race for Oregon secretary of state has prompted at least two particularly influential Democratic legislators, former House Majority Leader Jennifer Williamson and Senate Finance and Revenue Chair Mark Hass, to step aside to seek that statewide office.

In addition, multiple experienced lawmakers in their 60s, 70s and 80s have announced plans to retire.

Two Republican lawmakers who were appointed to their seats in the wake of former Sen. Jackie Winters’ death are expected to run for election to those positions for the first time in 2020.

And powerful Republican Sen. Cliff Bentz of Ontario has announced he will step down in January to run for Rep. Greg Walden’s seat in Congress.

Truckers and loggers opposed to the carbon capping bill rallied at the Capitol in June while Republicans were hunkered down out of state to prevent a vote on the measure.

Bentz and two Democratic senators who are retiring all played roles in killing a climate change bill that made international headlines this year. Bentz’ absence during the February 2020 short legislative session during which Democrats hope to take another run at a carbon cap-and-spend bill could color Republicans’ response.

Here are the seats that will be completely open or lack an elected incumbent in 2020:

Sen. Mark Hass, D-Beaverton, speaks in Senate chamber. He won't seek reelection to the Senate in 2020 because he is running for secretary of state.LC- The Oregonian

Beaverton’s Senate District 14: Hass, a three-term incumbent, is running in a crowded field seeking the position of secretary of state. After the death of Republican Secretary of State Dennis Richardson, former Republican lawmaker Bev Clarno is serving as an appointee for the remainder of his term.

The district is solidly Democratic. So far, veteran Washington County Commissioner Dick Schouten and Kate Lieber, a former Multnomah County prosecutor who now teaches criminal justice at Portland Community College, both Democrats, have filed to run for the seat. Schouten is married to a lawmaker in the House, Rep. Sheri Schouten, whom he proposed to during a floor session in 2017.

Gresham area’s Senate District 25: Sen. Laurie Monnes Anderson, 73, a fixture in the Legislature for two decades, will step down after completing her fourth Senate term in 2020. Environmentalists assailed Monnes Anderson after she joined two other Senate Democrats to kill a high-profile climate change bill earlier this year.

The district is solidly Democratic. So far, Rep. Chris Gorsek, D-Troutdale, whose House districtmakes up half the district has filed seeking his party’s nomination. That will leave an opening in House District 49.

Sen. Denyc Boles, who was previously appointed then elected to the Oregon House, plans to run in 2020 to be elected to the Senate seat to which she was appointed this year. Beth Nakamura / The Oregonian|OregonLive

Salem’s Senate District 10: Sen. Denyc Boles, a former short-term House member, was appointed to this seat after Winters died this year during her 21st year as a lawmaker. Boles has filed to run for the seat for the first time in 2020.

The district has a slight Democratic registration edge – 31% versus 30% registered Republicans – and is considered a swing district.

So far, one Democrat has filed to run against Boles: pastor and health care policy advocate Deb Patterson. Patterson was the Democratic nominee for the seat in 2018 but lost to Winters 46% to 54%. She has raised more than $24,000 this election cycle, including $15,000 from the largest state employee union, $7,500 from the Women’s Investment Network and $5,750 from MoveOn.org.

Another Democrat, Portland Urban League Executive Director Nkenge Harmon Johnson, has also created a campaign committee to run for the seat and has raised more than $8,500, most of it from her husband and other relatives. Although she works in Portland, Harmon Johnson was partly raised in Salem and still lives there.

Candidates have until mid-March to file to run for a Senate or House nomination in their party’s May primary.

Eastern Oregon’s Senate District 30: Bentz, who was elected to five terms in the Oregon House, was appointed and then elected in 2018 to the Senate to represent this sprawling district covering the eastern one-third of the state. Bentz will step down before the February 2020 short legislative session to be as competitive as possible in his primary race to succeed Walden in Oregon’s only Republican-held seat in Congress.

During this year’s legislative session, Oregon Senate Republicans, including Bentz, fled the state to prevent a planned vote on the Democrat-backed climate bill. They returned when Democratic leaders announced their party lacked the votes to pass it, because outgoing Sens. Arnie Roblan and Monnes Anderson, along with one other Democrat, opposed it.

Eastern Oregon Rep. Lynn Findley, left, shown with fellow Rep. Diego Hernandez, hopes he will be selected to replace Sen. Cliff Bentz, a fellow Republican, when Bentz departs the Legislature in January to run for Congress.LC-

Early next year, county commissioners from all around eastern Oregon will appoint a Republican to succeed him. Commissioners often choose to appoint one of the two House members who represent a departing senator’s district. Currently, those are Rep Daniel Bonham, R-The Dalles, and Rep. Lynn Findley, R-Vale.

Findley clearly hopes he will be the choice. He has filed to run for the seat in November 2020, meaning he will vacate his House seat.

Oregon Central Coast’s Senate District 5: Arnie Roblan, 71, a Democrat elected to two terms in this Senate seat after five previous terms in the Oregon House, will step down at the end of 2020. The former math teacher and high school principal has served in many powerful roles during his two decades in the Legislature, including co-speaker of the House, majority whip and co-chairman of the powerful budget-writing committee.

In 2019, Roblan played a central role in passing Democrats’ and public employee unions’ top priority, a $1 billion-a-year business tax to fund early childhood and K-12 education improvements. At the same time, he drew criticism from environmentalists and some in his own party for joining Monnes Anderson and Sen. Betsy Johnson, D-Scappoose, in blocking the controversial climate change bill.

The district is considered a Democrat-leaning swing district. In 2018, Roblan won a three-way race by just 349 votes.

So far just one candidate has filed to run for the seat in 2020, Democratic lawyer and Coos County Commissioner Melissa Cribbins. Of the two House members who represent portions of the district, one – Caddy McKeown, D-Coos Bay, 62 – has also announced her plans to retire. The other is David Gomberg, D-Otis, 66, who has been elected to four House terms.

Jennifer Williamson, former House Majority Leader, is running for Oregon secretary of state.

Northwest Portland’s House District 36: Williamson, like Hass, is seeking the Democratic nomination for secretary of state, hoping to succeed Clarno.

The district is considered solidly Democratic. Three Democrats have filed to run for the seat: longtime teachers union lobbyist Laurie Wimmer, pediatrician Lisa Reynolds and policy analyst and former House staffer Adam Meyer.

Gresham’s House District 50: Former Gresham Police Chief Carla Piluso, 63, a Democrat thrice elected to the seat, has said she will retire in 2020.

The district is solidly Democratic. So far, two Democrats have filed to run for the seat. Ricki Ruiz, 32, is a Gresham community services coordinator who was elected in 2017 to the Reynolds School Board. William Miller, is a former Oregon legislative assistant who now works as the advocacy manager for the Native American Youth and Family Center.

Bethany and Northwest Portland’s House District 33: Mitch Greenlick, 84, a medical policy expert, is serving his ninth straight term and plans to retire in 2020.

The district, representing northeast Washington County and parts of Northwest Portland, is solidly Democratic. Four Democrats have filed to compete in the May primary: education professor Andy Saultz; civil rights attorney Christina Stephenson; Serin Bussell, a former Metro analyst serving as chief of staff to Sen. Jeff Golden, D-Ashland; and doctor Maxine Dexter.

As of Thanksgiving, Saultz, who has raised $65,000, reported a $10,000 fundraising edge over his nearest opponent. His largest donors are Sen Elizabeth Steiner Hayward, who has given him $13,000 from her campaign fund, and two members of the Saultz family.

Oregon state Sen. Laurie Monnes Anderson, D - Gresham, plans to retire in 2020 after 20 years in the Legislature. Her departure makes room for a new senator from her Multnomah County district.Dave Killen / The Oregonian

Troutdale’s House District 49: Rep. Chris Gorsek, a community college instructor elected four times to represent the district, is opting to run for the Senate instead, hoping to replace retiring Monnes Anderson.

The district, which is solidly Democratic, spans Interstate 84 from Gresham to Troutdale. So far, one Republican and one Democrat have filed to seek the seat: Joe Demers, a Republican from Gresham who says he works in recycling and disposal, and Democrat Zach Hudson, a teacher at Reynolds High in Troutdale and a member of the Troutdale City Council.

Aloha’s House District 28: Rep. Jeff Barker, 76, plans to retire after 18 years in the House. One candidate has filed to seek the retired police officer’s seat representing Aloha: Democrat Wlnsvey Campos, a case manager with Family Promise of Beaverton.

Salem’s House District 19: Raquel Moore-Green, a former legislative aide, was appointed to the District 19 seat this year when Boles, who was in her first elected term representing Salem was appointed to fill Winter’s Senate seat. Moore-Green has filed to run for the seat for the first time, and one Democrat, self-described photographer and brand ambassador Sarah Landstrom, has filed for the Democratic nomination.

The district leans Republican, although not strongly so: 32 percent of registered voters are Republicans while 29 percent are Democrats.

Linn County’s House District 17. Sherrie Sprenger, R-Scio, has opted to run for a seat on the Linn County Commission in 2020 after being elected six times to represent District 17 in the House.

With the seat open, five other Republicans have filed to compete for the seat. Susan Coleman, Sprenger’s legislative assistant and a former Sweet Home city councilor, is one of them. The others are farmer Jami Cate; real estate broker and state property inventory specialist Bruce Cuff, who has repeatedly run unsuccessfully for governor; hardware store general manager Timothy Kirsch; and logging company executive Scott Sword.

South-central Coast’s House District 9: Four-term incumbent Caddy McKeown, 67, will step down in 2020.

The district is a Democratic-leaning swing district. So far, just one candidate, a Democrat, has filed to run for the seat. He is Mark Daily, a Coos Bay small business owner.

Rep. Carl Wilson, R-Grants Pass, center, appears at a 2015 hearing at the Oregon Capitol. He says 2020 will be his final year as a lawmaker.

Grants Pass’s House District 3: Former House Minority Leader Carl Wilson, 67, who was deposed from that caucus leadership position in September, says he’s ready to call it quits on a legislative career that spans six terms.

The district is solidly Republican. So far, just one Republican – Jordan Lawson, an advocate for people with disabilities – and one Democrat, disabled former Army National Guard member Jerry Morgan, have filed to run for the seat.

La Grande area’s House District 58: Republican Greg Barreto, 64, of Cove will step down after three terms.

The district, which spans Union and Wallowa counties and a portion of Umatilla County, is solidly Republican. So far, no candidates have filed to run for the seat in 2020.

Eastern Oregon’s House District 60: Lynn Findley was elected in 2018 to represent the largest House district in Oregon, District 60, which spans from Baker City all the way to the Nevada state line.

Findley was appointed to the post in 2018, then elected by voters that fall. He is now seeking the Senate seat that sweeps across all of Eastern Oregon being vacated in January by Sen. Cliff Bentz.

Findley did not file to run to represent his solidly Republican House district. Hay farmer and Harney County Commissioner Mark Owens did.

Note: This article was updated on Dec. 3 to include Barker among the representatives who plan to retire and to correct the name of the second House lawmaker whose district overlaps with departing Sen. Cliff Bentz’s.

-- Hillary Borrud; hborrud@oregonian.com; @HBorrud