State Senator Anthony Petruccelli, an East Boston Democrat widely considered a potential successor for the Senate presidency, is leaving the body to join a Boston lobbying firm.
Petruccelli's departure, as the state Senate adjusts to new leadership under Stanley C. Rosenberg, will likely touch off a special election in a district that includes East Boston, the North End, Beacon Hill, Revere, Winthrop, and parts of Cambridge.
Joining Kearney, Donovan & McGee, Petruccelli becomes part of an ever-lengthening parade of lawmakers leaving office but remaining on Beacon Hill. In the last several years, a handful of state senators once regarded as potential leaders of the chamber have stepped aside and taken lobbying jobs.
The firm's clients include insurers, Amazon, Comcast, and Yankee Atomic Electric Co.
Petruccelli said he would likely resign in January.
"I love my job as a state senator," he said in a telephone interview. "However, after almost 17 years of serving in the Legislature and over 20 years in public service, my family and I felt like this was the right time to move in a different direction of my life professionally and our lives as a family."
Petruccelli added, "While it is sad to give up something that I have done for so long and have been honored to do for the people who have elected me over the years, it is exciting to be transitioning into the private sector."
Petruccelli won a House seat in 1999 during a special election, then took the Senate seat in 2006, succeeding former Senate president Robert E. Travaglini.
When Rosenberg claimed the presidency earlier this year, Petruccelli was viewed as a potential chairman of the budget-writing Ways and Means Committee. But Rosenberg passed him over for Karen Spilka, an Ashland Democrat. Petruccelli instead became the Senate's majority whip, the sixth-ranking position on the leadership ladder.