MILTON — This leafy suburb bordering a rough edge of Boston may be the hardest-won district in Massachusetts in Thursday’s primary election. No fewer than nine Democratic hopefuls are vying for two open seats in the Legislature created by the departure of longtime Senator Brian A. Joyce.

Representative Walter F. Timilty of Milton is vacating the House seat he held for nine terms (and Joyce occupied before him) to run for the Senate. And seven Democratic contenders have emerged to try to claim the open House seat.

“I haven’t seen this much activity in 30 years,’’ said Milton resident Joe Lally. “There are signs all over town for the candidates.’’

In the Senate primary, Timilty faces a fierce challenger: newcomer Nora Harrington, who also lives in Milton and has built her campaign around the notion that the district deserves a new voice.

“I think it’s important we send some new people to Beacon Hill,’’ Harrington told a voter on Churchill Street in Milton on Friday. “New energy.’’

One way or another, change is coming to Milton; Joyce’s exit demands it. Early this year, he announced that he would not seek election for the first time in 20 years.

The FBI had raided his Canton law office, and the Globe reported that a grand jury was investigating whether he had used his Senate seat to advance his private law practice. Campaign regulators had also found he had charged his political campaign fund for his son’s high school graduation party.

The combative Democrat had few friends on Beacon Hill but maintains the loyalty of many of his constituents for his years of service and advocacy in the district.

But no one is expecting a tidy baton pass to Timilty, his House counterpart.

Suffice it to say there is no love lost between the two pols. Joyce made his start in politics by ousting a 30-year incumbent legislator who was an ally of Timilty’s political family. Some people never forgot.

Timilty denied any bad feelings dating back to Joyce’s first race, but he was unsparing as he pointed to the allegations against Joyce’s ethics.

“I believe that there’s been a cloud over the Senate district for quite some time because of Senator Joyce’s actions,’’ Timilty said. “And I’m not a yes man for anybody.’’

An affable 47-year-old born into a political family, Timilty insists he is not taking the election for granted.

He has been knocking on voters’ doors all over the district and on Friday, he visited voters in Sharon, where voter Anne Bingham told him that she’s not involved in politics, “but I know your name is good.’’ (The Senate district covers parts of Sharon, Easton, and Braintree, as well as Avon, Canton, Milton, Randolph, Stoughton, and West Bridgewater.)

But his upstart challenger is making the same argument against longevity that Joyce once employed to great success. One of Harrington’s campaign mailers calls her as “the antidote to the career politician.’’

Not everyone is buying it. As Harrington made her pitch for change to one voter last week, the woman bemoaned the changes that have already come to Milton and remarked how nice Timilty is.

Traditions die hard in Milton, a town of 27,000, where many have roots in the machine politics and the parishes of the big city next door. One voter told the Globe he’d probably vote for Timilty, “because I know who he is.’’

Harrington acknowledged, “I had one woman on the other side of town tell me, ‘We want someone who’s from here.’ I wasn’t born and raised in Milton.’’

Born to Irish immigrants in the Bronx, Harrington moved to Massachusetts for Williams College more than 30 years ago and settled in Milton later.

With her partner, Andrea Piatt, a clinical neuropsychologist, Harrington founded Commonwealth Psychology Associates, a behavioral health group practice with four area locations; Harrington serves as chief operating officer.

Though she is a first-time candidate, she is not unfamiliar with the campaign trail. She canvassed for Democrat Martha Coakley’s unsuccessful campaign for US Senate and for state Senator Linda Dorcena Forry’s first election for state representative.

Harrington also worked as a professional fund-raiser for nonprofits for years and raised money for political candidates, including Hillary Clinton.

On the trail and in her campaign literature, Harrington argues that she’s the one who will fight for “true Democratic values,’’ including abortion rights and LGBT rights.

Timilty, who opposes abortion, has a more conservative record on social issues. When gay marriage was contested on Beacon Hill, he voted to put the question before voters on the ballot — which gay activists resisted, saying civil rights should not be put to a popular vote.

Timilty maintained on Friday that he didn’t “vote against marriage equality. I voted to put it on the ballot to let the people decide,’’ he said. He added that he’s now “quite happy with the law of the land,’’ legalizing same-sex marriage.

“I’m a moderate guy,’’ Timilty said, defending his record. “I’m concerned about all the issues that affect the people in the district.’’

He frowned upon the negativity of Harrington’s campaign literature and her focus on his record, rather than her own proposals. “My opponent’s very focused on myself as opposed to being focused on issues that I believe are important to all of us,’’ Timilty said.

Harrington has circulated a postcard saying Timilty has “17 years on Beacon Hill with little to show for it but a history of right-wing votes’’ and that he has “brought home a tiny 1 percent of the funding he’s requested’’ to the district.

She said she needs to contrast her views with those of her opponent in mailers because Timilty did not participate in any debates. Harrington appeared in numerous forums with an independent candidate, Jon Lott, who will face the winner of Thursday’s primary in the November election.

As Timilty vacates his House seat to run for Senate, seven Democrats from the Milton and Randolph district are vying to replace him. The field includes William J. Driscoll Jr., Tony Farrington, Kerby Roberson, Denise R. Swenson, and Michael F. Zullas, all of Milton; and Jason R. Adams and James F. Burgess Jr., both of Randolph.

The House race is expected to drive up turnout in Milton.

Timilty says the focus on his hometown is fine by him.

“I like the high turnout in Milton,’’ he said. “I’ve worked for Milton and Randolph now for a long time. And I’m a hands-on state rep.’’

Stephanie Ebbert can be reached at Stephanie.Ebbert-@globe.com. Follow her on Twitter @StephanieEbbert.