For the first time in 16 years, Dartmouth voters will see an additional name on their ballot for Bristol County District Attorney during the September primary.

Shannon McMahon, a former Bristol County prosecutor, announced Wednesday that she will run against fellow Democrat Thomas Quinn III, who is seeking a third-term as the county’s top solicitor.

McMahon said her reason for running is because “a lot of people are unhappy” with the state of the county.

“The current administration has not been focused on that because it does not understand the communities, which have changed,” the democratic challenger said. “We must change with it.”

McMahon, a resident of Swansea, attended UMass Law on Faunce Corner Road between 2008 and 2012 where she clerked for Superior Court Judge Robert Kane and was elected editor-in-chief of the UMass-Dartmouth Law Review.

Upon graduation, McMahon clerked at the superior courts in Taunton, Fall River, and New Bedford.

After completing her clerkship, McMahon worked for the Bristol County District Attorney’s Office in New Bedford’s drug recovery court during the onset of the opioid crisis.

She currently works as a trial attorney in Raynham.

If elected, McMahon said one of her top priorities will be to reduce the rates of repeat offenders. 

To achieve this, she said she plans to work with the Bristol County Sheriff’s Office and local police departments to help former inmates get counseling when out of jail or prison.

“Traditionally, this has not been done,” McMahon said. “After the verdict, no one has paid any attention to the individuals when they return to our community until they commit another crime. This is a travesty and I believe we can do far better.”

The candidate said she also hopes to expand the county’s drug court to help addicts find treatments rather than go to jail. She also proposed a Mental Health Court to deal with what she said is a “huge mental health crisis.”

“If people can’t get help, they’re more likely to commit crimes,” she said.

Quinn, a native of Dartmouth, is currently seeking a third term as DA. He ran unopposed in his last two elections.

He was appointed as acting DA by then-Gov. Deval Patrick and current Gov. Charlie Baker in 2015 to replace Sam Sutter, who himself ran unopposed in two elections.

The last contested DA’s race was in 2006.

The two-term DA is touting his public record to the voters of Bristol County, including his convictions in the high-profile cases of Aaron Hernandez and Michelle Carter.

Quinn also highlighted his creation of a special unit of the DA’s office devoted to solving cold cases.

This past December, his office indicted former Dartmouth resident David Reed on charges related to the murder of his half-sister in 2001. Testing of the interior of a conch shell believed to be the murder weapon revealed a full DNA profile that matched Reed’s.

With regard to the opioid crisis, Quinn said his office is working with local partners to address the epidemic, along with domestic violence and teen safety issues.

“My priority is the safety of the citizens of Bristol County,” he said “People have a right to feel safe in their communities.”

McMahon said while it might be daunting to go up against a long-term incumbent, she’s “ready to work.”

“We’ve got a lot of doors to knock on,” she said

The primary will be held on Sept. 6.