BOSTON — Treasurer Deborah Goldberg seemed to be all in on a run for Congress in the 4th Congressional District. And then she wasn't.

Goldberg, the two-term state treasurer, said Wednesday night that she would not be a candidate for the seat currently held by U.S. Rep. Joseph Kennedy III, and instead she was "committed to the impact and possibilities" at Treasury.

"I was going to run because I knew I could be a direct and unambiguous voice that would cut through the noise. However, our work here is too important and I will find a new avenue to combat the injustice I see in our country and our world today," Goldberg said in a statement.

The decision by the Brookline Democrat to pass on the rare, wide-open campaign for a seat in Congress caught many of her friends and advisors off guard.

The 65-year-old Democrat had filed the paperwork to set up a federal campaign committee and commissioned a poll that showed she would be the early frontrunner.

After taking time with family during the Rosh Hashanah holiday to weigh her decision, people close to Goldberg said that as recently as Tuesday night she was telling friends she was leaning toward getting in. Her political team had a full campaign ready to go, including a speech and a campaign schedule.

And then she changed her mind.

"I am committed to the impact and possibilities here at the Treasurer’s office, and what we are accomplishing for the people of Massachusetts. From the roll out of our baby steps college savings plan in 2020 to the expansion of our economic empowerment programs that help seniors, veterans, women and children, I simply cannot walk away. Our work is not done," Goldberg said.

Goldberg's decision to pass on the race completely scrambles the dynamics of a field that so far does not include anyone with a profile as big as the treasurer's.

So far, four candidates have formally entered the race, including City Year co-founder Alan Khazei of Brookline, Newton City Councilor Becky Grossman, former Wall Street regulator Ihssane Leckey of Brookline, and Jesse Mermell, the recent past president of the Alliance for Business Leadership and former Deval Patrick communications advisor.

Mermell officially launched her campaign in Fall River on Wednesday afternoon and had a house party planned in Brookline at night.

Other potential candidates moving toward a run in Kennedy's district include Newton City Councilor Jake Auchincloss and Dave Cavell, a former Obama speechwriter who stepped down from his position as senior advisor in the Attorney General's office last week to assemble a campaign in preparation for a possible run.

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