Top Walsh aide Daniel Koh among potential candidates for Niki Tsongas’ seat

With US Representative Niki Tsongas’ annoncement that she is not seeking re-election next year, the floodgates of Massachusetts political ambition have suddenly swung open.

Democrats and Republicans across the Third District — which encompasses all or part of almost 40 communities including Lowell, Lawrence, Methuen, Haverhill, and Andover — are revving up long-dormant congressional aspiration.

“Anyone who is holding political office will think about it. And there will be lots of people from the private sector, too. It’s a great and rare opportunity,” said former state senator Steven C. Panagiotakos of Lowell, who was one of the few current or former politicians with ties to the district to rule out a run for the seat.

The district, which includes tony towns like Concord and working-class urban centers like Lawrence, leans Democratic. Hillary Clinton won it with 57 percent to Donald Trump’s 35 percent in last year’s presidential election, according to the nonpartisan Cook Political Report. As a result, much of the chatter has focused on which Democrats might run, according to interviews with several political operatives who know the district and the players.

Insiders see Daniel Koh, Mayor Martin J. Walsh’s chief of staff, as a likely Democratic candidate. A 32-year-old Andover native with an elite resume — Harvard College, Harvard Business School, Huffington Post — he has acknowledged thinking about running for political office, and he has long been seen as eyeing a congressional bid.

Asked if Walsh or Koh, a Boston resident, wanted to weigh in on the chatter, City Hall spokeswoman Laura Oggeri declined to comment. (Candidates for Congress do not have to live in the district they hope to represent.)

State Senator Barbara A. L’Italien, Democrat of Andover, released a statement saying she is “eagerly exploring the opportunity of running for this Congressional seat and how to best continue in Niki’s footsteps as an indefatigable advocate for the priorities of the women, men, and children of the 3rd District.”

And state Senator Eileen M. Donoghue, a Lowell Democrat who came in second to Tsongas in the 2007 Democratic special election primary for Congress, said she is going to talk with her family about running for the US House again.

“I’m truly stunned. This is a shock,” she told the Globe Wednesday. “I can’t say for certain what I will do. I hadn’t given it much thought but I’ve been asked to look at it.”

Still, in a hint of where her political desire may be, Donoghue said, “I’m really enjoying my time in the Senate.”

Senator James B. Eldridge, an Acton Democrat who also ran in the 2007 primary, said he is considering a run.

“At this time in our nation’s history, we need, more than ever, bold, progressive, visionary leadership in the Democratic party and among our Democratic elected officials,” said Eldridge, one of the senate’s most liberal members.

State representative Jennifer E. Benson, a Lunenburg Democrat, is mulling a run, according to a person familiar with her thinking. A voicemail left with an aide wasn’t returned.

Private citizens are also in the Democratic mix.

Michael W. Gallagher, a prominent Lowell lawyer, one-time school committee member, and co-chairman of Tsongas’ campaign finance committee, said running to succeed the Congresswoman “is certainly of interest to me.”

In a short telephone call, he said: “If your question is: would I entertain it? Absolutely.”

Plenty are former officials, looking to get back in the game, who are thinking about a run.

Stephen J. Kerrigan, the 2014 Democratic nominee for lieutenant governor and an unsuccessful candidate for party chairman last year, is considering throwing his hat in the ring, according to a source familiar with his thinking.

And former state senator Barry R. Finegold of Andover said in a statement he is thinking about a run.

“Having once served a portion of this district, I am intimately aware of the local issues, and will be taking some time with my family to consider a decision regarding this race,” Finegold said.

On the Republican side, Rick Green, a wealthy auto parts company executive from Pepperell, is seen as a leading contender for the Republican nomination for Congress if he runs.

He is the co-founder, with his brother, of 1A Auto Inc., which sells auto parts online and offers free YouTube videos about how to install them. While coy about his wealth, he told the Globe last year 1A Auto has well over $100 million in annual revenue.

Green, who ran for GOP party chairman in 2013, also founded the Massachusetts Fiscal Alliance, a nonprofit loathed and feared by Beacon Hill Democrats who see it as a GOP front group. He did not respond to a text message and voicemail.

Gardner Mayor Mark P. Hawke, a Republican who has led the city of 20,000 since 2008, is seen as a serious contender if he were to enter the race. Reached Wednesday, the mayor said he was surprised by Tsongas’ announcement and hasn’t given any thought to a congressional run.

Businessman Salvatore Lupoli, the founder and president of Lupoli Companies, which includes Sal’s Pizza, is seriously thinking about a bid for the Republican nomination, according to someone familiar with the Chelmsford resident’s thinking.

State Representative Sheila C. Harrington, a Groton Republican, and Ann Wofford, who was the GOP nominee against Tsongas last year, were floated as potential candidates.

A voicemail left with a Harrington aide and a message left on a number associated with Wofford went unreturned.