Spilka has focused on troubled children, families throughout career

Karen Spilka, who has claimed the votes to be president of the Senate, is poised to become one of the state’s most powerful political figures.Suzanne Kreiter/Globe Staff/File 2015/Globe staff

Karen Spilka says life in her house was unpredictable and scary. Growing up in Yonkers, N.Y., with a father who struggled with mental illness, she never knew when she got home whether he would be angry or happy.

“I often look back on my past experiences and wonder, ‘Why did my life turn out the way it did?’ ” Spilka once said. “To be more blunt, I often ask myself, ‘Why am I not more messed up?’ ”

The answer, she says, is that her volatile father forced her to become stronger, and to learn how to read people and pick up clues about their behavior. He also, she says, gave her a sense of empathy for others who struggle with problems beyond their control, and an inclination to defuse, rather than escalate, conflicts.

Those qualities shaped her professional life, leading her into a varied career as a social worker, labor lawyer, mediator, and legislator who has sought to help troubled children and families find stability without ending up in the criminal justice system.

Now, Spilka, a 65-year-old Democrat from Ashland, is poised to become one of the most powerful figures on Beacon Hill.

Last week , she claimed to have enough votes to become the next Senate president, a role that will make her one of the most significant forces in state policymaking, along with House Speaker Robert A. DeLeo and Governor Charlie Baker.

She sees the position as the culmination of her past experiences, and an opportunity to continue to advance the Senate’s liberal agenda against the more conservative House and governor.

“I loved all my other jobs, my past work,” Spilka said an interview. “But this is such an incredible opportunity to combine all my background – personal, professional — and really work with my colleagues to help make a difference for the people of the Commonwealth.”

As president, she will face a daunting challenge trying to stabilize a 40-member chamber that has been riven by internal power struggles since December, when Stanley C. Rosenberg stepped down as Senate president amid allegations that his husband sexually harassed and assaulted four men and meddled in the Senate’s official business.

In an indication of the delicate task she faces, Spilka and the current Senate president, Harriette L. Chandler, who took over from Rosenberg in December, disagreed publicly on Thursday about when the actual transfer of power will take place.

At an awkward press conference, Chandler said she wants to serve until her term expires in January, but Spilka declined to endorse that timeline, saying she wants to discuss the issue further. Privately, some senators want Spilka take over sooner, rather than have Chandler serve as a lame duck for the next 9 months.

“It’s curious that she’s got the votes almost a year before the election is scheduled to take place — a lot can change in 9 months,” said former Senate president Thomas F. Birmingham, who said he understands why Spilka might want to take over sooner and why Chandler doesn’t want to step down early. “That’s a challenge because you can’t have two Senate presidents.”

Whenever Spilka does take the gavel, admirers say she will draw on her experience as a mediator to listen to her colleagues and let them help set the agenda.

She will also use her knowledge of the Legislature’s internal workings. She has served for 17 years on Beacon Hill, and has helped craft the state budget as chairwoman of the powerful Senate Ways and Means Committee since 2015.

“She’s a good choice,” said former Senate Republican leader Richard R. Tisei. “The Senate obviously turned to a steady hand and somebody who is well-versed on the budget and most major issues. She obviously has some depth and knowledge, which I think is going to be very important.”

Spilka grew up as one four children in a family she describes as apolitical. Her mother was a social worker. Her father served in World War II and was injured when he stepped on a land mine — a battle scar she believes contributed to his mental illness. A builder by trade, he struggled financially when the construction industry suffered, she said.

Her younger sister, Susie, was born with Down syndrome, and Spilka later became her legal guardian. She died last year after suffering from Alzheimer’s disease.

Spilka says she got the political bug in high school when she was elected sophomore class president. After graduating from Cornell University in 1975, she spent two years working in Boston as a school social worker.

She entered Northeastern University Law School hoping to study juvenile justice but switched to labor law, considering it a better fit for her skill set.

After being admitted to the bar in 1981, she worked as a lawyer representing unions, and then took a job with the state office that negotiates collective bargaining agreements — an experience she says is still helpful to her as a legislator. She was also the first labor and employment lawyer at the Massachusetts Water Resources Authority.

She entered politics in 1999, after moving from Cambridge to Ashland with her husband, Joel Loitherstein, an environmental engineer. After serving on several town boards, she won a seat on the Ashland School Committee, and formed a coalition to lobby the Legislature to change the formula used to disburse education aid, convinced that it shortchanged certain suburban districts.

In 2001, her state representative resigned, “and within about 10 seconds, I thought ‘Wow, I can make better change from within than from without,’ ” so she decided to run for the seat. “I called up my husband and he said, ‘Go for it,’ ” Spilka said.

Spilka served in the House until 2005, when she was elected to the Senate.

During her time in the Legislature, she helped create the Office of the Child Advocate, a watchdog agency that oversees the child welfare system.

She also helped overhaul the CHINS (Child in Need of Services) law that allowed parents to petition courts for help for their troubled children, amid criticism that it was trapping too many families in the criminal justice system. The new system, called Children Requiring Assistance, is designed to provide more services for young people who run away from home, disrupt school, or cannot obey their parents.

Spilka has also fought to raise the age at which juveniles can be tried as adults to 21.

Spilka has said her own tumultuous childhood convinced her “it is unfair for us to expect [children] to ‘grow up just fine’ when they have no supports, and cruel to punish them for the behaviors that follow when no one helps them.”

Josh Dohan, who heads the Youth Advocacy Division of the Committee for Public Counsel Services, worked with Spilka to overhaul CHINS, and said it required her to bring together prosecutors, court officials, defense lawyers, and advocates who were often at odds.

“What I experienced is somebody who is confidently reasonable,” Dohan said. “She didn’t pound her fists. She said, ‘I hear what you’re saying, and let’s talk about how to get past that.’ She invited people to participate, even when we were not getting our way in the moment.”