The Massachusetts state Senate will install its third leader in eight months Thursday when it votes to elevate Ashland Democrat Karen Spilka to the Senate Presidency.

The Massachusetts State Senate has been riding a roller coaster for months. A sitting president resigned after his husband triggered a sex scandal. The chamber’s senior member stepped in to fill the void. A federal raid brought down another top Democrat. Tomorrow, the Senate will make what members hope is the last major change when it elects 65-year-old Spilka as the 95th leader of the upper chamber.

Spilka is, by action and by trade, a professional mediator. The former social worker and labor attorney takes pride in her history of sitting at negotiating tables, alongside parties with disparate goals, and coming out the other side with a solution in hand.

"I used to train people in mediation, in listening, active listening skills. And how to get folks to come to an agreement, what are their real positions, what are their issues that they want resolved," Spilka told WGBH News in an exclusive interview this week.

Spilka said she's trained to get past people's posturing and cut to the center of matters and "what are the underlying hard issues that they need and want to have resolved."

Spilka was a social worker before attending law school and starting her own labor arbitration business. In 2001 she won a special election to the House of Representatives and moved over to the Senate in 2004 where she's risen through the ranks.

Former Senate President Therese Murray, the Senate's first female leader, knows what it's like trying to move the inflexible levers of legislative power. She says Spilka will bring that mediator experience to the all-important weekly Monday afternoon closed-door meetings between the governor, the Speaker and the Senate President.

"Those Monday meetings in particular, where you bring up all the main things the three branches want to move forward.... She'll certainly hold her own in those and put her imprint in that and the imprint of the Senate," Murray told WGBH News.

At 65 years old and the mother of two grown sons and an adult stepdaughter, Spilka already has a lifetime of experience outside of the State House. The learning curve for her new job, begins at the hectic tail-end of the legislative session. When it's over, she has to prepare for the new session in January. Key to all of this will be reaching a working accomodation with her legislative partner and peer, House Speaker Robert DeLeo.

The Senate and the House have been at odds on a number of legislative matters this year, including immigration and school funding. Some think the two chambers are further apart at the end of this session than in recent years.

Spilka might see these differences as opportunities to mediate compromise with the Speaker.

"I feel very comfortable and I'm actually looking forward to working with Bob on this level and I think it'll be an exciting time for the Legislature," Spilka said of DeLeo, who will enter his 11th year at the helm of the House in January.

Spilka's legislative confidence comes from her work as chair of the Senate's Ways and Means Committee, the powerful budget-writing panel that alongside it's House counterpart, holds the pursestrings for state spending.

"[Spilka's] coming from a position of wide knowledge of some of the issues the state's facing and that's a real plus in a Senate president," said Framingham State University Political Science Professor David Smailes, a constituent of Spilka's from Framingham. Smailes adds that Spilka has developed a reputation as a hard worker both in her district and the halls of the State House.

The chamber Spilka will take over, rocked by the resignation of President Stan Rosenberg last year, has stabilized under the leadership of caretaker president Harriette Chandler. That leaves Spilka the challenge of getting the Senate's ambitiously progressive agenda not only out of her branch, but past Baker and DeLeo, and into law.

As Spilka settles into the presidency, the excitement is likely to focus on whether Massachusetts should declare itself a "sanctuary state" and how to make good on promises to improve local school funding.

Getting the sluggish Legislature to pass bills the left-leaning Senate advocates will take buy-in from voters and activists as well as legislators.

"To me, the other issue that's really important is an overarching theme of justice. Whether it be social, civil and economic justice and civil rights I think that's something we can never lose sight of," Spilka said.

As she ascends the Senate's rostrum and takes the gavel from Chandler, Spila is taking it in stride.

"I consider myself to some extent an improbable senator, let alone senate president. This isn't something I ever planned on doing. And I've come to deeply love the Senate and the work that I do,"

Improbable or not, Spilka has jumped out of the frying pan and into the fire. The question now is will she be consumed by the heat? Or will it energize her?