She has a PhD in international relations and an MBA, and has never lost an election in a legislative career that began more than two decades ago, when Bill Weld was governor.
But few outside of her Worcester district had heard of Harriette L. Chandler until she was chosen this week to serve as acting president of the Massachusetts Senate, replacing Stanley C. Rosenberg, who stepped down as he faces an ethics investigation stemming from allegations that his husband sexually assaulted and harassed four men.
Chandler’s abrupt elevation makes the liberal Democrat, who turns 80 this month, the Senate’s lead negotiator in weekly meetings with House Speaker Robert A. DeLeo and Governor Charlie Baker, sessions where many of the thorniest decisions are hashed out by Beacon Hill’s three major players.
Senators said she was chosen for the unusual assignment because she is a seasoned, competent legislator who has promised not to hold on to the presidency permanently, allowing the Senate to function with as little disruption as possible as it endures its biggest leadership crisis in recent years.
She will have to lead the chamber during a period of extraordinary anxiety and uncertainty, a job made all the more challenging as several younger, more ambitious senators openly jockey for the presidency, should the office become vacant.
“My biggest challenge is to regain our balance,” Chandler said in an interview Wednesday. “This is a body blow we’ve taken, to have this happen to the office of the presidency.”
Chandler has said she will serve as president until the Senate completes its investigation of Rosenberg — an unknown period of time that could stretch well into 2018, when the Senate will be negotiating with the House and the governor to complete a new state budget and finish bills affecting criminal justice, health care, and other issues.
“The challenge is to make sure the Senate is on equal footing in any discussions around policy,” said Senator Barbara L’Italien, an Andover Democrat. “I don’t want to see us getting distracted and getting nothing accomplished for the rest of the year.”
Chandler, who has been Senate majority leader since 2015, said she has never attended any of the weekly leadership meetings with the governor and House speaker, but she served with DeLeo in the House and has worked with Baker.
She said she is determined to help the Senate finish its work on criminal justice, health care, and other priorities that were launched under Rosenberg.
“I am not trying to set my own agenda,” she said. “I’m following the agenda that the Senate set.”
Several colleagues said she is well-suited for the job.
“People really feel like she’s a compassionate person, she’s experienced, she has great relationships, she’s admired, and, of course, she is not seeking to be the permanent president, and that made people feel comfortable she can step into this role on a temporary basis,” said Senator Jason M. Lewis, a Winchester Democrat.
She brings to the interim assignment an extensive educational background and a history of fighting for women’s issues, abortion rights, and access to health care.
Born in Baltimore to a nurse and a lawyer, Chandler graduated from Wellesley College in 1959 but didn’t run for office until she was in her 50s.
After teaching high school in Worcester, she wrote a doctoral dissertation on US-Soviet relations during World War II and got her PhD from Clark University in 1973. Ten years later, she received an MBA from Simmons College.
Chandler, known as Harlee, has been married for 58 years to Burton Chandler, a lawyer known as Buddy. They have three grown children.
In his self-published memoir, “Small Town Lawyer,” Burton Chandler recalls, in a chapter titled “And Then There is My Wife,” that he represented Harriette in a federal lawsuit alleging sex discrimination by Brown University, after it turned her down for a tenure-track position more than 30 years ago. Harriette Chandler received a $9,500 settlement.
She was elected to the Worcester School Committee in 1991, to the House in 1995, and to the Senate in 2000, after defeating Joseph D. Early Jr., now the Worcester district attorney, in a hard-fought race for an open seat.
Over the years, Chandler has sponsored laws that allow women to obtain restraining orders against strangers, not just family members or romantic partners; that guarantee women can stay at least 48 hours in the maternity ward after giving birth; and that expand “buffer zones” to keep protesters away from abortion clinics.
Chandler, whose annual salary is $157,540, has said she will decline an additional stipend as Senate president and continue to work in her own office, even though Rosenberg is vacating the president’s ornate suite.
She said she is planning to run for reelection next year and then return to her regular role in the Senate.
“I truly look forward to this being accomplished and behind us,” she said. “I didn’t want to be Senate president. I didn’t seek it. And it sought me, actually.”Michael Levenson can be reached at mlevenson@globe.
com. Follow him on Twitter @mlevenson.