California will see history made on Wednesday as Toni Atkins becomes  the first woman and first lesbian to hold the top job in its senate.

A former Assembly speaker, Ms Atkins is taking over the post of senate president for the time being from fellow Democrat Kevin de Leon as the chamber gears up for election season and faces thorny challenges.

These include a reckoning over sexual misconduct, a loss of the Democratic super-majority and an icy relationship with the state Assembly.

Sen Atkins, right, talks with Sen Holly Mitchell at the Capitol in Sacramento, California (Rich Pedroncelli/AP)
Sen Atkins, right, talks with Sen Holly Mitchell at the Capitol in Sacramento, California (Rich Pedroncelli/AP)

Ms Atkins, whose colleagues describe her as measured, said she is not focused on making headlines.

“I think you’re going to see my focus will be internally so you’re not going to get any big pronouncements,” she said.

Senate Democrats lost their super-majority last month when Los Angeles-area Senator Tony Mendoza resigned rather than face a very rare expulsion vote over sexual misconduct allegations, although he is running again for the same seat.

Critics have said that with sexual misconduct, the statehouse culture values the protection of lawmakers over justice for victims.

They said incidents of inappropriate behaviour are swept under the carpet, and an inconsistent, haphazard investigation process leads victims to suffer in silence for fear that coming forward would only harm them.

Sharp disagreements over handling sexual misconduct investigations, a single-payer health care bill and other issues of style and substance have driven a wedge between the Senate and Assembly.

Ms Atkins said her early work will be focused on running the Senate, including developing a process to deal with sexual harassment allegations.

Other efforts to put her stamp on the senate, like reshuffling committee assignments, will come later.

Mr De Leon took control of the Senate in 2014 but is barred by term limits from seeking re-election and is challenging Democratic US senator Dianne Feinstein.

Ms Atkins will have an unusually long run in the senate’s top job if she keeps the support of fellow Democrats, as she is not term-limited until 2024.

Ms Atkins, who has pushed forward groundbreaking legislation on health care, LGBT rights and housing, is described by colleagues as kind, measured and compassionate but steadfast in her commitment to fighting for people and ideas she believes in.

“When people first interact with Toni, what they see is a very unassuming, low-key person who has a bit of an earth mother effect about her,” said Senator Scott Wiener, a San Francisco Democrat.

“People sometimes mistake that for weakness. But what they don’t see is right underneath that surface is pure steel. She is tough as nails. But she has a huge heart.”

Ms Atkins, 55, is in her first four-year term as a senator after six years in the Assembly, where she also set a milestone as the first openly gay woman to serve as speaker.

Mr Wiener, who is gay, said having a member of the LGBT community in one of the state’s most powerful positions will ensure that issues they face do not take a back seat now that same-sex marriage is legal.

Originally from Appalachian Virginia, Atkins moved west and was a health care administrator in San Diego before turning full time to politics.

Last year, Ms Atkins was a driving force behind a successful push to raise money for subsidised housing by charging 75 dollars (£54) for many real-estate transactions.

She was also the co-author of a contentious bill that would replace traditional health insurance companies with a single government-funded health care plan for everyone in the state.

She wrote a bill signed by Governor Jerry Brown to create a “non-binary” gender option on driver’s licenses for people who do not identify themselves as male or female.

Sen Pat Bates, a Republican from Laguna Niguel and the Senate minority leader, said she is hopeful Ms Atkins will give Republicans more say in which committees they are assigned to and more notice before taking up legislation on the floor.

Sen Holly Mitchell, a black Los Angeles Democrat, said: “I’m thrilled that after over 100 years, when I walk down that corridor leading to the Senate floor that there will be a woman’s portrait there on the wall.

“I’m really excited to be a sitting member of the senate when we make history.”