Democrat Justin Brannan scored a resounding victory Tuesday night, besting his Republican opponent, Ari Kagan, by 17 points in the race for a southern Brooklyn City Council seat.

But Brannan said that was despite the efforts of the Brooklyn Democratic Party — more specifically, chairwoman Rodneyse Bichotte-Hermelyn, who publicly denounced him a week before Election Day over years-old allegations of harassment.

“Amplifying the talking points of my opponents, and some of just the most ghoulish trolls that are out there — the fact that she was amplifying them and giving those attacks credence is pretty unforgivable,” Brannan said in an interview on NY1’s “Mornings On 1” Wednesday.

“It’s very disappointing that Justin Brannan feel that way,” Bichotte-Hermelyn said in an interview.

She said the county organization supported Brannan with phone-banking and door-knocking; the Brannan camp said that’s categorically false.

And Bichotte-Hermelyn, again, pointed to allegations of bullying made by an autistic former co-worker of Brannan.

Brannan denies the allegations, but Bichotte-Hermelyn said he needs to be held accountable.

“First of all, I think he needs to apologize,” she said. “I think he needs to apologize, maybe take some classes, in terms of being able to work on his behavior, in terms of harassment and bullying.”

Brannan allies remain outraged that the Brooklyn Democratic leader would actively undermine the Democrat in perhaps the city’s most hard-fought race. And the intra-party warfare seems unlikely to blow over just because Brannan won on Tuesday.

“People are scratching their heads. It’s incredibly disturbing,” said state Sen. Andrew Gounardes of Brooklyn. “I have not called for Rodneyse’s resignation yet, for her to step down. But I think a lot of people are expecting that, are thinking that, and wondering who can lead this party moving forward.”

Bichotte-Hermelyn, who’s also a state assemblywoman, said she was celebrating her party’s wins across Brooklyn Tuesday — including Brannan’s.

“I was very happy that he won because we’re all Democrats at the end of the day,” she said.

The question now is whether an increasingly public rift in the party can be repaired.

“It’s just not acceptable for a Democratic leader to act this way, contrary to the only job they have, which is to support Democrats in their home county,” Gounardes said.