On sexual misconduct, critics say the statehouse culture values the protection of lawmakers over justice for victims. They say incidents of inappropriate behavior are swept under the rug, 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.
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, she said.
De Leon took control of the Senate in 2014. He's barred by term limits from seeking re-election and is challenging Democratic U.S. Sen. Dianne Feinstein.
If she can keep the support of her fellow Democrats, Atkins will have an unusually long run in the Senate's top job; she isn't term-limited until 2024.
Atkins, who has advanced groundbreaking legislation on health care, LGBT rights and housing, is described by her 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 affect about her," said Sen. 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."
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. Wiener, who is gay, said having a member of the lesbian, gay, bisexual and transgender community in one of the state's most powerful positions will ensure that issues they face don't take a backseat 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.
"San Diego, while the second-largest city in California, we're treated as if we're a backwater when it comes to funding and equal access," said Sen. Joel Anderson, a Republican who represents suburban and rural areas of San Diego County. "Having a pro tem from Diego will give San Diego great gravitas in getting treated equally with all the other communities in California."
Last year, Atkins was a driving force behind a successful push to raise money for subsidized housing by charging $75 for many real-estate transactions. She also was 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 Gov. Jerry Brown to create a "non-binary" gender option on driver's licenses for people who don't identify as male or female.
Sen. Pat Bates, a Republican from Laguna Niguel and the Senate minority leader, said she's hopeful Atkins will give Republicans more say in which committees they're assigned to and more notice before taking up legislation on the floor. The GOP, she said, is often left in the dark.
Sen. Holly Mitchell, a Los Angeles Democrat who is black, said the portraits of past presidents pro tem all look remarkably familiar; before de Leon, who is Latino, they were all white men.