After a hard-fought race against a two-term Republican congressman, Democrat Andy Kim was officially declared the winner of New Jersey's Third Congressional District seat in his first bid for public office, and his opponent, Rep. Tom MacArthur, said Wednesday night that he had called Kim to concede.

"Tonight, I called Congressman-Elect Andy Kim to congratulate him on his victory," MacArthur, 58, wrote in a Facebook post shortly before 7 p.m. "Enough provisional ballots have been counted to make the outcome clear. My staff and I will work with him to ensure a smooth transition in every way."

Kim, a former national security aide to President Barack Obama, had declared victory on Nov. 7, a day after the election, after Vote-by-Mail ballots put him ahead of MacArthur, a former insurance executive and an ally of President Trump.

The Associated Press declared Kim the winner at 2:44 p.m. Wednesday, though election boards in Ocean and Burlington Counties have not completed counting provisional ballots.

Kim's victory means that New Jersey will have only one Republican in its 12-member congressional delegation in January: U.S. Rep. Chris Smith, who won reelection.

When Kim takes office in January, it will be just the second time in at least 34 years that Democrats will hold the South Jersey seat. He also will be the first Asian American elected to the House from New Jersey, and the first Korean American elected to Congress in two decades.

"This campaign was never about the politics," Kim said in a statement Wednesday. "It was always about the people of New Jersey and who would best advocate for the hopes and needs of our community in Washington. Our campaign was about the issues — about affordable health care for all Americans; about fair taxes for New Jersey families; and about a government that works for the people."

Kim pledged that he would work on those and other issues "while representing my home district with integrity and civility in Washington."

Wednesday night, one week after Kim declared victory in a Mount Laurel campaign office crowded with supporters, MacArthur said in the statement that he was proud to have represented the district "with honesty and integrity," and that he and wife Debbie's commitment to helping others "has never been defined by politics or elected office."

"I am also a firm believer that good can come out of life's disappointments, and I look forward to what the future holds for us," said MacArthur.

Kim, 36, of Bordentown, had declared victory when he edged ahead by 2,600 votes out of about 295,000 tallied. His margin had grown to 3,427 after all of the mail-in ballots were counted, along with about 1,000 machine ballots that were not delivered by poll workers to election headquarters in Burlington County on election night.

In recent days, Kim had conducted himself as if victory was assured — he has been in Washington this week joining fellow election winners in an orientation for incoming House members.

About 7,000 provisional ballots in the race are still being counted and are expected to determine the official winner in the next couple of days. Some election officials have said Kim's lead would continue even after the count because most of the provisional ballots are from Democratic-leaning Burlington County. The Third District is comprised of the majority of towns in Burlington and some towns in Republican-leaning Ocean County.

MacArthur said in a statement last week that he wanted to wait for the final tally before he would make an announcement. On election night, as his supporters waited for him to speak at his watch party in Toms River, he declined to address the crowd.

Tom MacArthur, the Republican candidate in New Jersey’s Third Congressional District, District, spoke during an October debate with Democratic candidate Andy Kim in Newark, N.J.
Julio Cortez, AP File
Tom MacArthur, the Republican candidate in New Jersey’s Third Congressional District, District, spoke during an October debate with Democratic candidate Andy Kim in Newark, N.J.

MacArthur at one point was seen as a potential Republican candidate for governor or Senate, and early in his congressional career, he focused on crafting a centrist image that fit with the tradition in the moderate South Jersey district.

But as Trump took office and the GOP took control of Congress, MacArthur not only supported Trump's attempt to repeal the Affordable Care Act, he forged a compromise with the hard-right Freedom Caucus that helped revive the effort after it appeared dead.

The move thrust MacArthur into the national spotlight. He had a speaking role at a Rose Garden ceremony alongside Trump after the House passed the repeal plan, but it also roused fervent opposition within his district — including from some voters who previously supported him and later became dedicated to his defeat.

MacArthur was the only Republican in the Philadelphia area to back the repeal of the health-care bill, and his deal cost him a leadership slot in the centrist GOP Tuesday Group.

MacArthur later became the only New Jersey lawmaker in either party to support the tax bill, which limited the deduction for state and local taxes — a valuable and popular provision in the Garden State. He negotiated for a cap on the deduction, rather than a full elimination.

In both cases, MacArthur became  part of high-level talks in Washington. For someone in just his second term, he enjoyed an outsize role in influencing major legislation and was seen as a deal maker. He argued that by not just offering a blanket "no," he could help shape the bills to make them better.

But the attention brought a backlash and helped power Kim's campaign. Critics accused MacArthur of undermining vital health care safeguards and supporting a tax bill that could cost his constituents.

On Wednesday, the counting of provisional ballots continued into the evening. Ocean County had 2,400 provisional ballots to consider. It disqualified about 20 ballots that were cast by voters who had already submitted a Vote-by-Mail ballot before showing up at the polls. It also debated whether to ask a judge to decide whether 45 provisionals that were brought to headquarters in an unsealed bag should be counted.

The Ocean County Board of Elections hand counts more than 2,000 provisional paper ballots in the tight Andy Kim-Tom MacArthur race for a seat in New Jersey’s Third Congressional District.
Connor Smith / Staff
The Ocean County Board of Elections hand counts more than 2,000 provisional paper ballots in the tight Andy Kim-Tom MacArthur race for a seat in New Jersey’s Third Congressional District.

In Burlington County, Superintendent of Elections George Kotch sent about 4,500 provisionals to the Board of Elections Wednesday morning after his staff had spent 10- to 13-hour days since Saturday analyzing them to see if they were valid.

Kotch said about 95 percent of the provisionals were deemed eligible to be counted and were stamped "registered voter" in red before they were turned over to the board.

Burlington County Superintendent of Elections George Kotch standing in front of copies of the ballots on the desk behind him, and the bags used by polling places are on the floor.
JESSICA GRIFFIN / Staff Photographer
Burlington County Superintendent of Elections George Kotch standing in front of copies of the ballots on the desk behind him, and the bags used by polling places are on the floor.

Board Chairman Joseph Dugan said Wednesday that the board would begin its count on Thursday morning.

"We expect to have it done by the end of the day, possibly late into the night," Dugan said.

The Region Turns Bluer

With Andy Kim’s victory in New Jersey’s Third Congressional District, the region’s congressional districts have become more heavily Democratic compared with two years ago. Use the slider below to compare the two maps. Pennsylvania’s districts were redrawn earlier this year by the state Supreme Court.
JOHN DUCHNESKIE / Staff Artist

Staff writer Amy S. Rosenberg contributed to this article.