A day after an election-night standoff, Democrat Andy Kim claimed victory to a seat held by Republican U.S. Rep. Tom MacArthur after thousands of mail ballots tallied by Burlington County election officials gave him the lead in New Jersey's hotly contested Third District congressional race.

"With the vast majority of votes now in and counted, and based on the numbers we saw from Burlington County today, we have built a substantial lead," he told supporters crowded into his headquarters in a Mount Laurel office park Wednesday night. "I am proud to announce that we have won this hard-fought race."

The two-term incumbent, however, did not concede, issuing a statement saying, "This has been a hard-fought campaign and like Andy Kim, I'm ready to see it come to an end." He said he would await the final count, including 7,000 votes he said were  outstanding.

If the lead holds in official returns, Kim would become the fourth New Jersey Democrat to win a seat previously held by a Republican in Tuesday's midterm election, joining Mikie Sherrill in New Jersey's 11th, Tom Malinowski in the Seventh, and Jeff Van Drew in the Second.

MacArthur, 58, was a big target for Democrats. He encountered a surge of suburban activism and an electorate's deep anxiety over health care in his quest for a third term.

Kim, 36, faced months of relentless attacks in two media markets by MacArthur and allied super PACs.

A former insurance executive, MacArthur was the only New Jersey congressman to vote for the tax bill, which capped deductions on state and local taxes, and helped craft an amendment that rescued the ultimately failed attempt to repeal the Affordable Care Act. Though he stressed bipartisan credentials, he was the New Jersey congressman most closely aligned with President Trump's agenda.

Kim, a Rhodes scholar who worked as a national security adviser for the Obama administration, moved back to the Marlton area, where he was raised, to run for Congress.

Tom MacArthur, the Republican candidate in the U.S. Congressional District 3 race, speaks to reporters after a debate with Democratic candidate Andy Kim, Wednesday, Oct. 31, 2018, in Newark, N.J.
Julio Cortez
Tom MacArthur, the Republican candidate in the U.S. Congressional District 3 race, speaks to reporters after a debate with Democratic candidate Andy Kim, Wednesday, Oct. 31, 2018, in Newark, N.J.

The additional votes counted from Burlington, the Democratic half of a district that also includes the Republican-leaning Ocean County, gave Kim a 2,600-vote lead out of about 295,000 votes tallied in the district.

The new total allowed Kim to overtake the 2,300-vote lead MacArthur took away election night, when the congressman left his Toms River headquarters without addressing supporters gathered there, and both campaigns called the race too close to call. 

Kim, for his part, took the stage shortly after 12:30 a.m. Wednesday at his Mount Laurel hotel gathering and told supporters, "We can win this thing."

Twenty hours later, Kim stood before a music stand and cameras and said: "It is an honor and a privilege to be the next congressman of the New Jersey Third Congressional District.

"I promise you I will be part of that new generation of leaders that are going to step up and focus on what's best for the American people, what we can do for all of us," he said to supporters, some of whom were tearing up.

Democrat Andy Kim hugs NJ Senator Troy Singleton before announcing that he is the projected winner of the NJ 3rd District Congressional race. The announcement was before a packed crowd at his Mt. Laurel headquarters on Nov. 7, 2018.
ELIZABETH ROBERTSON / Staff Photographer
Democrat Andy Kim hugs NJ Senator Troy Singleton before announcing that he is the projected winner of the NJ 3rd District Congressional race. The announcement was before a packed crowd at his Mt. Laurel headquarters on Nov. 7, 2018.

New totals showed Kim with 101,903 votes in Burlington County, an increase of 14,487 votes over previous totals.

MacArthur's totals also increased, but by 9,550, to 69,090 in Burlington County.

Burlington County Clerk Tim Tyler said he believed Kim's 32,000- vote margin in the county — mirroring MacArthur's advantage in Ocean County — was significant. He said he did not expect the results to change once several thousand provisional votes were examined and then counted if found legitimate.

Poll workers also failed to turn in all of the voting cartridges in five districts on election night, but Tyler said that should have little impact on tallies. Based on experience, he said, some of the cartridges may be blank if some of the voting machines in a district were not used. Cartridges were not turned in by districts in Riverside, Mansfield, Pemberton, Evesham, and Chesterfield.

Democrat Andy Kim stands with his family after announcing that he is the projected winner of the NJ 3rd District Congressional race. The announcement was before a packed crowd at his Mt. Laurel headquarters on Nov. 7, 2018.
ELIZABETH ROBERTSON / Staff Photographer
Democrat Andy Kim stands with his family after announcing that he is the projected winner of the NJ 3rd District Congressional race. The announcement was before a packed crowd at his Mt. Laurel headquarters on Nov. 7, 2018.

Joseph Dugan, the chairman of the Burlington County Board of Elections, said the county received 26,000 mail-in ballots this year, perhaps twice as many as last year and more than in 2016, a presidential election year. He said poll workers counted 20,000 of them on Election Day, from 7 a.m. to 10 p.m., and resumed counting the remaining 6,000 on Wednesday.

Election workers on Wednesday were busy removing them from envelopes and putting them in piles behind closed doors in a three-story county office building across from the  courthouse. Dugan said their next chore would be to break the plastic seal on the canvas bags that contained the paper provisional ballots delivered by each voting district after polls closed.  Next, they would turn them over to the superintendent of elections, on the second floor, so that he could match them up with voting registration records and see if the ballots are valid, Dugan said.

On Wednesday afternoon, lawyers and party officials milled around and waited for the tallies to be announced.

An official winner might not be declared for days, as officials in both Burlington and Ocean Counties also have to process provisional ballots, which are given to voters who show up at polls despite having received a mail ballot, among other reasons. In Ocean County, vote-by-mail ballots were included in the Tuesday night totals, county officials said.

The race broke the way pollsters had predicted: an essential standoff between Ocean County to the east, with its many retirees and solid Republican base, and Burlington County across the river from Philadelphia, where Democratic registration has increased significantly in the last two decades, said Benjamin Dworkin, a political science professor at Rowan University.

The surge in Democratic voting in Burlington County on Tuesday was enough for voters to take over long-held Republican county offices. Places like Willingboro, where voting is typically light in midterms, saw heavier turnout and even waits at some polling places.

In addition, newly organized progressive groups like Action Together New Jersey, and its Burlington and Ocean Counties spinoffs, spearheaded extensive vote by mail operations in the last year.

Uyen Khuong, who founded the Action Together group after the 2016 election, said Wednesday the group's thousands of volunteers used a database (and their own stamps) to target nearly 300,000 voters statewide in 16 weeks. This "Post-it posse" sent out applications for vote-by-mail ballots, along with a Post-it note urging voters to consider voting by mail, which New Jersey allows for any reason.

In the Third Congressional District, Khuong said, 82,000 applications were sent out.

Democrat Andy Kim announces that he is the projected winner of the NJ 3rd District Congressional race. The announcement was before a packed crowd at his Mt. Laurel headquarters on Nov. 7, 2018.
ELIZABETH ROBERTSON / Staff Photographer
Democrat Andy Kim announces that he is the projected winner of the NJ 3rd District Congressional race. The announcement was before a packed crowd at his Mt. Laurel headquarters on Nov. 7, 2018.

She said she alerted state and county officials ahead of time to print extra ballots, telling them, "I'm going to do a huge push to change the voting habits of New Jersey voters."

The number of vote-by-mail ballots also increased significantly this year because of a new law that required all voters who had voted by mail in 2016 to receive a mail ballot for this election.

Ocean County Republican Chairman George Gilmore blamed the law, and Gov. Murphy, for creating confusion and requiring voters to use provisional ballots when they arrived at the polls and were told they were a "vote-by-mail" voter.