Anne Caravone, 73, and her husband Albert, 74, who live in Hillsboro, said that recent political protests in Portland, some of which grew violent or destructive, had disturbed and frightened them, and left them questioning Democratic control of so many offices across the state. Ms. Caravone, who said she tends to vote for Republicans, said she was undecided in her vote for governor, but had ruled out Ms. Brown. Mr. Caravone said he was leaning toward Mr. Buehler, but in the end might leave that part of his ballot blank.

Ms. Brown, some voters said, has also suffered by comparisons to her once popular predecessor, Mr. Kitzhaber, who was the longest-serving governor since Oregon’s statehood in 1859. Mr. Kitzhaber resigned in 2015, a few weeks after starting his fourth term, amid accusations that his fiancée, Cylvia Hayes, had used her access to gain consulting contracts. No criminal charges were filed against either Mr. Kitzhaber or Ms. Hayes, who had been an unpaid policy adviser to the governor, but the Oregon Ethics Commission concluded that both of them had violated conflict-of-interest laws.

Mr. Kitzhaber had an unquestioned, if sometimes mocked, star power, often looking like he had stepped out of a Ralph Lauren ad, wearing an almost constant uniform of cowboy boots, jeans and a sport jacket.

By contrast, Ms. Brown, who is 58 and the nation’s first openly bisexual governor, leans toward what one supporter called a “Portland anti-style,” — plain clothes, sensible shoes and clunky glasses that tend to slide down her nose. As secretary of state, Ms. Brown was first in the line of succession to Mr. Kitzhaber since Oregon has no lieutenant governor. Then Ms. Brown won a special election in 2016. This is her first time seeking a full four-year term.

“I’ve heard people say, ‘I don’t feel energized by her,’” said Ms. Howard, who said she plans to vote for Ms. Brown. “People don’t say that about male candidates,” Ms. Howard added.

Mr. Buehler, an orthopedic surgeon, has made the pitch to voters that he would be a pragmatist governor, aiming to address Oregon’s problems the way he was trained as a doctor — diagnosing issues and addressing them with logic, not partisanship. His television ads have attacked Ms. Brown’s performance on everything from the state’s handling of mental health to child welfare.