A day after Andy Kim claimed victory in the tight race for New Jersey's Third Congressional District seat against Republican incumbent Tom MacArthur, scores of election workers were frantically working behind the scenes Thursday to finish counting thousands of ballots.

As of Thursday, the vote was 148,580 for Kim; 145,958 for MacArthur — a  2,622-vote lead for the Democrat, but about 9,000 ballots are still waiting to be analyzed.

"We're really busy here, I can't take any more questions," said a frazzled Joseph Dugan, chairman of the Burlington County Board of Elections, who waved his arms as reporters surrounded him.  "We have people working hard in a small room in the back, and I can't have cameras in there to make it even more confusing."

Kim, a newcomer to politics, said Wednesday night he felt his margin of victory was substantial enough to declare himself the winner, while MacArthur said in a statement he would wait until the last votes were counted.  He said that there were 7,000 outstanding votes, but that figure changed Thursday as Vote by Mail and provisional ballots, and votes in cartridges, were counted.

The Third District includes towns in Democratic-leaning Burlington County and Republican-leaning Ocean County. Kim prevailed in Burlington by about 32,000 votes, while MacArthur won by about 30,000 in Ocean.

Election officials in Burlington County say the 9,000 uncounted ballots may have minimal impact. There were more provisional ballots cast in Burlington County than Ocean, and ballots that were not counted on election night when poll workers failed to deliver them on time to election officials come from heavily Democratic districts.

On election night, officials in the two counties initially reported that each had about 3,000 or more provisional ballots. Burlington County has 4,800 and Ocean has 2,404. These are paper ballots given to voters whose names don't appear in the poll books. The ballots are inspected by the county superintendent of elections to see if the voters were eligible to cast a ballot. It's a time-consuming chore, and some election officials  predict it might not be finished until Wednesday or later.

In Burlington, about 1,000 votes weren't calculated on election night due to "human error," according to the county clerk. Poll workers in voting districts in five towns didn't deliver the cartridges in a timely fashion.

In addition, 500 new Vote-by-Mail ballots arrived from the post office on Wednesday and Thursday, according to Dugan. The  Ocean County Board of Elections reported it had received a total of 308 Vote-by-Mail ballots from the post office in the last two days. Any ballots received within 48 hours of Election Day can be included as long as they were postmarked by Election Day.

At MacArthur's election watch party, GOP Chairman George Gilmore, who is also Ocean County's superintendent of elections, said the election would be close and MacArthur would not address the crowd because there were too many votes that were not tallied.

During his announcement, Gilmore said was "confident Tom has won" but later added that that was his opinion based on the votes that were in.

On election night, MacArthur was up by about 2,300 votes. But that lead evaporated Wednesday afternoon when Burlington County released its mail-in totals. Kim received the majority of those 26,800 mail-in votes: 14,487. Ocean County had included mail-in votes in its election night tally.

Now the focus is on provisional votes. Election officials in both counties were checking databases to see which ones can be counted.

"The doors are closed, and they're still counting votes and holding meetings," said an employee at the Ocean County Board of Elections.

In Burlington County, Superintendent of Elections George Kotch said Thursday he had just received the 4,800 provisional ballots from the Board of Elections to review. "This will take a couple days to do, and we will probably work through the weekend," he said. Kotch said he must manually look at the paper ballots and compare them against a list of registered voters to see why their names didn't appear in the poll books at polling places throughout the county. Ballots will be disqualified if a voter is a convicted felon, is not registered properly, or received a Vote-by-Mail ballot.

Under a new law, anyone who voted in the 2016 election with a mail-in ballot was automatically mailed a Vote-by-Mail ballot this year. Anyone on that list who showed up at the polls was given a provisional ballot to prevent voting twice.

Burlington County Deputy Clerk Wade Hale said he has been examining about 1,000 ballots that were not counted on Election Day because the voting cartridges in five districts were not delivered to the county superintendent in a timely fashion. Hale said that poll workers in districts in Riverside, Mansfield, Pemberton, Evesham, and Chesterfield did not deliver all of the cartridges that were supposed to come in that night.

After receiving a verbal court order from Superior Court Judge Ronald Bookbinder on Wednesday night, Kotch was authorized to open the voting machines that contained those cartridges and he turned them over to Hale to review.

Hale said some of the cartridges were blank — they were inside machines that were not used on Election Day. Another cartridge had jammed and Hale used the backup tape to tally those votes. Two other cartridges, he said, were found in poll worker bags instead of being delivered with the others on a cartridge rack. "Not a single vote was lost," he said.