Each blamed the other for running a nasty campaign.
"Nobody knows who he is," said candidate Ras Baraka.
"We don't need him," said Shavar Jeffries, his opponent.
The two men are vying for the seat held by Cory Booker from 2006 until he was elected to the U.S. Senate last year. Former councilman Luis Quintana has served as interim mayor since January. The election will be held May 13.
While the major polling institutes in New Jersey haven't weighed in on the race, Baraka acknowledged that Jeffries may have made some headway with a recent flurry of ads.
"When you're spending $2 million to talk negatively, there's going to be some movement," he said. "The real poll is on election day. On election day we're going to see that those polls are wrong."
The race has become a brawl, and Wednesday night's debate was only the latest round.
"The more he talks, the worse things get," said Jeffries, who took the offensive against the veteran Newark Councilman Baraka.
Baraka portrayed Jeffries as an opportunist with no history in Newark politics. "I've never seen you involved ... where have you been?" he said. "Newarkers, we've seen this movie before."
Both sides lobbed accusations of campaign finance shenanigans Tuesday. A video of Baraka speaking to gang members also became a focus over allegations that it was derogatory toward the city's Latino residents.
Dueling news conferences 90 minutes apart, one by a group supporting Shavar Jeffries and another by Baraka, culminated in a spirited, but civil, street confrontation between members of both groups outside a Baraka campaign office.
The Associated Press contributed to this report.