It took until 9 o’clock on Tuesday morning for his opponent to concede, but interim Suffolk District Attorney Kevin Hayden had claimed victory on Tuesday night in his bitter Democratic primary against Hyde Park Councillor Ricardo Arroyo, following weeks of backbiting and vicious volleys that spilled into other political arenas and eroded public trust in the office.

According to unofficial tallies, Hayden won Boston, Revere and Winthrop, while Arroyo won Chelsea. In Boston, with one precinct still left to report, Hayden won 36,950 votes (53 percent) while Arroyo garnered 32,000 ballots (46 percent). City elections officials reported 644 write-in votes.

The result ends a pitched battle for the seat, a campaign that was rocked by separate reports in the Boston Globe that alleged Hayden had mishandled an investigation of Transit Police officers involved in a Mattapan roadway incident while Arroyo had been investigated for sexual assault as a teenager.

Hayden and Arroyo denied the respective accusations and ignored ensuing calls to resign. Arroyo faced a collapse in political support, as Mayor Michelle Wu and US Sen. Elizabeth Warren pulled their endorsements.

After the polls closed, Hayden supporters, including Dorchester Councillor Frank Baker, state Sen. Lydia Edwards and Councillor At-Large Erin Murphy, flocked to SoWa Power Station in the South End. “I promise I won’t let you down,” Hayden told them.

Gov. Charlie Baker in January appointed Hayden, a Roslindale resident, as interim DA after Rachael Rollins left for the US Attorney’s Office. Hayden ran to serve out a full term.

Before the appointment, Hayden served for six years as chairman of the state’s Sex Offender Registry Board. His resume also includes stints as a criminal defense attorney and a Suffolk County assistant district attorney.

Arroyo, a district city councillor from Hyde Park, is the son of Register of Probate Felix D. Arroyo. First elected in 2019, Councillor Arroyo previously worked as a public defender for the Committee for Public Counsel Services.

On Wednesday morning, Arroyo allowed that he had lost, saying, “With nearly all the votes counted it is clear we do not have a path to victory.”

He had thanked his supporters, who had gathered at the Dona Habana restaurant by Boston Medical Center, on Tuesday night.

“This has been a difficult campaign, not just in the last two weeks but from the very beginning,” he said. “And the reason this was a difficult campaign from the very beginning is because many of those most impacted by this justice system, most disillusioned by this justice system, had a hard time understanding why it was even worth investing their energy and their time to try to turn what has been largely a harmful system for our communities into something that might be less harmful.”