Six months after state Senator Frederick E. Berry announced plans to retire after this term, a wide-open race for the veteran Peabody Democrat’s Second Essex seat is kicking into gear.

With last Tuesday the deadline to file nomination papers with the secretary of state’s office, four Democrats and a Republican have officially entered the running in the district, which includes Beverly, Danvers, Peabody, Salem, and Topsfield.

As the district’s first contest for an open seat in three decades — Berry was first elected in 1982 — the race promises to be one of the year’s most closely watched in the region.

Another factor thrusting it into the limelight is that the field includes three relatively well-known contenders: Fifth District Governor’s Councilor Mary-Ellen Manning and former state representative John P. Slattery, both of Peabody; and Salem City Council president Joan B. Lovely.

These three and a last-minute entrant, former Fifth District governor’s councilor Edward J. Carroll of Salem, will vie in a Sept. 6 Democratic primary.

An emerging point of contention is which candidate could most effectively advocate for the district at a time when it is losing the special clout Senator Frederick E. Berry wields as a 15-term senator and the chamber’s number two leader.

The winner will compete in the Nov. 6 final election with Richard A. Jolitz, a Beverly Republican who unsuccessfully challenged Berry in 2010.

Arthur Powell, a Democratic State Committee member from Beverly, predicts a competitive Democratic primary.

“They’ve all shown an ability to raise money and to gather support,” he said, referring to Lovely, Manning, and Slattery. “They are out there. They are working hard. They are having events. I think each candidate is to be taken seriously.”

An emerging point of contention in the race is which candidate could most effectively advocate for the district at a time when it is losing the special clout Berry wields as a 15-term senator and the chamber’s number two leader.

“Fred’s got 30 years of experience and he’s built relationships in the Senate. No one can walk in and have that kind of effective voice right at the beginning,” said Slattery, an attorney who served four terms as a state representative, from 1995-2003, and lost bids for lieutenant governor in 2002 and mayor of Peabody in 2005.

But Slattery said he has “a proven ability to get things done that will benefit the district,” citing his role as chief sponsor of an assault weapons ban and an early teacher retirement bill both adopted during his time as a legislator.

“If elected, I can walk in and hit the ground running and be effective for the financing needs of the district,’’ Slattery said.

Manning, a practicing attorney who is in her sixth term as governor’s councilor, said, “I think I’ve established myself as somebody who is able to deliver a message that resonates with people.

“Before I was a governor’s councilor, many would suggest that no one had ever heard of the office. I’ve made efforts at reforms that have had enough of an impact to raise the office on the average person's radar. . . . And I think I've been an independent voice.”

Lovely, a practicing attorney in her eighth term as a city councilor, emphasizes her municipal government background.

“I know how decisions that are made on Beacon Hill affect residents and our communities. . . . I understand how the process works and I believe that experience will help me at the State House to be able to represent the whole district,” she said.

Lovely spent two years on Beacon Hill as an aide to the late state Representative J. Michael Ruane of Salem.

After he retired in 2004, she lost a primary bid in the race to succeed him.

“I’ve been going door to door, and health care is on the top of people’s minds,” Lovely said.

Noting that the Legislature is considering House and Senate proposals to rein in health costs, she said, “I want to be part of that process as the next state senator.”

Slattery, a former one-term Peabody city councilor, said, “My passion has always been education,” pledging to continue to make that a priority.

He said he would also focus on the needs of seniors and work closely with local municipal leaders on their objectives.

Manning said she would work to reduce waste in government in order to provide tax relief, including for small businesses, and to provide more funding for “programs that the entire district would benefit from.”

She said education would be a priority for her, including expanding support for English as a second language classes for adults.

Another would be continuing the advocacy Berry has long provided for people with mental and physical challenges.

“What we should be doing is looking to cut waste across the board to preserve much-needed programs and safety nets for people,” said Manning, whose sister is Peabody City Councilor Anne M. Manning-Martin.

Carroll, who as a Lynn resident served one term as governor’s councilor — from 1993-95 — retired seven years ago as deputy superintendent of housing at the Essex County Correctional Facility in Middleton.

“Now that I'm retired — I'm 72, in the elderly stage — I want to bring a voice for the retired senior citizen,” he said. “The federal government wants to cut meals on wheels, and in our backyard the [MBTA] wants to go up on the RIDE from $2 to $4. . . . I just want to keep a close eye on” those and other issues of concern to seniors.

Jolitz, a paramedic and dispatcher for an ambulance company in Newburyport, said he is running as someone who can help bring a shift in priorities to state government.

“Massachusetts has seen some tough times here the last few years, especially when it comes to job growth. . . . And we are not seeing much change coming out of Beacon Hill to make this a more business-friendly environment in the state, especially when it comes to regulations,” he said.