It'll be a few more days before election officials in Burlington County determine if Democrat Andy Kim's victory celebration was premature or not.

The Burlington County Board of Elections will begin counting provisional ballots by hand later this week, either late Thursday or early Friday. But first, elections Superintendent George Kotch must determine how many of the 4,571 ballots are valid.

The outcome will provide the final tally of the hotly-contested 3rd District congressional race between incumbent GOP Rep. Tom MacArthur and his challenger, Kim.

Kim held a lead of 3,424 votes over MacArthur -- 150,311 to 146,887 -- at the end of last week. He pulled ahead when mail-in ballots were counted Wednesday, the day after the election.

Andy Kim, the Democratic challenger in New Jersey's 3rd District congressional race, holds his son Austin Kim, as addresses the media after voting (AP Photo/Mel Evans) AP

"Andy has an insurmountable lead that we believe will only grow as the last ballots are counted," Zack Carroll, Kim's campaign manager, said Tuesday.

Kim gave a victory speech last week in front of a crowd of boisterous supporters.

A request for comment Tuesday from MacArthur's campaign was not immediately returned.

We did it! Posted by Andy Kim for Congress on Wednesday, November 7, 2018

The 3rd district also includes parts of Ocean County, where MacArthur so far won 16 of the 17 towns, taking 61 percent of the vote. Officials in Ocean County will begin counting valid votes among 2,404 provisional ballots there on Wednesday.

Provisional ballots are issued on Election Day for voters who experience discrepancies, such as their names not being on the registered voter list at the polls. This year, many voters who were registered to vote by mail and either didn't receive the ballot or didn't send it in were also given the option of a provisional ballot.

The district stretches between Burlington County in the Philadelphia suburbs and Ocean County along the Shore, but neither county lies entirely within the 3rd district. Portions of the provisional ballots cast in both counties were in races in other congressional districts.

The 3rd district has largely been held by the GOP for the past three decades. But, the odds of MacArthur pulling off a win this year seem slim.

Here's our back-of-the-napkin math:

Roughly 1,400 of Ocean County's provisional ballots were cast in the 3rd district race. If the same percentages hold up for the provisional ballots as did in the rest of the ballots cast, MacArthur stands to gain about 850 votes there and Kim another 550.

But in Burlington County, MacArthur only got about 40 percent of the non-provisional votes. If the same percentage holds up, he'll only get another 1,700 votes from the provisionals cast in the 3rd district race there.

Between the two counties, that could be another 2,500 votes. But, based on how the vote went so far, Kim could pick up that many in Burlington County's provisionals, alone.

Two years ago, MacArthur took home about 53 percent of the vote in Burlington and 68 percent in Ocean.

Kim's strength in Burlington County was part of a wave that will put Democrats into control of county government for the first time in 45 years.

Kim is set to become the first Korean-American congressman from New Jersey and the state's 12-member congressional delegation will include only one Republican, four fewer after the election.

That's the lowest total for Jersey House Republicans since the 1912 election - the same year Fenway Park opened and the Titanic sunk.

Bill Duhart may be reached at bduhart@njadvancemedia.com. Follow him on Twitter @bduhart. Find NJ.com on Facebook.

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