With 102 of the 518 provisional ballots disqualified Tuesday, Guardian's victory appeared secure.
It would be "numerically impossible" for Langford to catch up, said Michele Verno, an attorney representing Guardian's campaign.
Langford representative Wilbur Banks, however, was not saying it was over. "Stick around," he said.
The other race in question, for the Second Assembly District, was still awaiting provisional-ballot counting, though with mail ballots tallied, incumbent Republican John Amodeo's lead of nearly 300 votes had shrunk.
The validation and count of mail-in and provisional ballots in the two races began with a promise by the board chairwoman that the process would be "long and arduous."
"We are not about chilling the vote but instead about encouraging the vote," said Paula S. Dunn, one of two Democrats on the four-member board.
The count continued into the night.
Hanging in the balance was the slender lead held by Guardian, who claimed victory over Langford on election night after Langford gave what sounded like a concession speech.
The provisionals yet to be counted were from heavily Democratic areas, but whether those were Langford votes awaited the tally. The board accepted an additional 68 mail-in ballots Tuesday.
Langford sat for a brief time at the back of the courtroom at the old courthouse and said, "I just want to see the process unfold."
Guardian's supporters lined the rest of the back row, but Guardian himself did not appear in the courtroom.
Also watching the process was Northfield Mayor Vincent Mazzeo, the owner of a popular fruit and vegetable shop.
In the Assembly race, Democrat Mazzeo began the day trailing Republican Amodeo by nearly 300 votes, with 1,167 provisional ballots and an additional 93 mail ballots yet to be counted.
With the mail ballots counted, Mazzeo had closed the gap to 194 votes.
Around 5 p.m. the board began going through provisional ballots, which had been sorted and investigated by county Superintendent of Elections Maureen Bugdon. Many were rejected on grounds that the voter was not registered or that a mail-in vote already had been cast.
Bugdon said the back-to-back special and general elections had confused some voters who did not remember whether or for which election they had sent in a mail-in ballot.
The focus on the board's examination of the paper ballots followed a long holiday weekend of accusations of misconduct from both sides.
Democrats accused Republicans of deliberately postponing the meeting from last Friday so they could use the weekend to canvas Atlantic City to verify provisional voters, likening the effort to voter suppression.
The state had set Nov. 12 as the date for the Board of Canvassers to meet in all counties. Republicans said they were doing nothing improper in preparation for the examination of the provisional ballots.
For their part, Republicans accused Democrats of using a petition about the minimum wage increase to disguise a request for a mail-in ballot, leading to the high number of provisional ballots that needed to be issued. They asked the state attorney general to investigate.
Guardian, 60, an openly gay former Boy Scout executive who has been in charge of the city's Special Improvement District for two decades, continued to work on his transition, said Mark Pedula, head of the city's Republican Party.
Guardian drew on a base of support from a wide-ranging tableau of new and old Atlantic City: Pakistanis, Vietnamese, Bangladeshis, African Americans from Langford's own neighborhood, and young white hipster entrepreneurs.
His unexpectedly strong performance against the entrenched Democratic power in a city where Democrats outnumber Republicans 9-1 electrified his supporters, who see him as able to work with the state, governor, and casinos while being intimately familiar with the city. He lives in the Inlet section and rides a bike to work.
Langford, a two-term mayor who has famously clashed with Gov. Christie over Sandy and tourism, and defended black neighborhoods against encroachment from the casino industry, blamed his predicament on complacency among his supporters.
He described his election night speech as a "concession of sorts" and told radio host Harry Hurley last Wednesday that "I would rather be in the position that he's in than the one I'm in."
The board defines provisional ballots as those issued to "voters if the poll book was marked 'voted by mail' and the voter says he/she never received, lost, or was otherwise unable to vote by mail; if a person has moved less than 30 days prior to election, or if a person has changed his/her name."