Hundreds of mail-in ballots challenged by Republicans in New Jersey's hotly contested Third Congressional District race will be counted, two judges ruled Tuesday afternoon.

Burlington County Superior Court Judges John E. Harrington and Mark P. Tarantino ruled that the ballots will be open and counted but kept separated in case there is an appeal, said Joseph P. Dugan, the chair of the Burlington County Board of Elections.

Dugan, a Democrat, sided with the other Democratic board member, Alice Furia, in defending the ballots for which the Democrat state committee had helped voters apply. Christopher L. Baxter and Michael A. Eaton, the Republicans, had disagreed. With the four-member board split along party lines, the decision went to Superior Court.

The decision affects 843 mail-in ballots, Dugan said.

Judges began hearing testimony on the issue around 11 a.m. Tuesday.

"It was involved. A lot of work had to go into it," Dugan said. "The judges had to put a lot of time into it."

The Burlington County Republican committee had challenged the ballots last Friday in a filing, saying they should be invalidated because the Democrat state committee left out required information when sending mail ballot applications.

In the U.S. House race between the GOP's Tom MacArthur and Democrat Aimee Belgard, one of the most hotly contested in the region, Democrats sent mail-in ballot applications to registered Democrats and other likely Belgard voters. Those applications, sent in October, were prefilled with required voter information.

Recipients could send the application in and then receive a ballot to vote by mail, a method campaigns often encourage because of its ease. New Jersey allows mail-in voting for any reason.

But Democrats did not fill in the "assistor" section of the applications, required in cases where a voter receives help. The forms asked for an assistor's name, signature, and mailing address.

The county Board of Elections says on its website, citing state law: "Any voter may receive assistance in making application for a Vote by Mail Ballot, but if any person assists the voter in completing any part of a vote by mail application, the name, address and signature of the person assisting must be provided."

Democrats acknowledge they did not fill out the section but called it a "technical oversight" and framed the Republican challenge as an attempt to disenfranchise supporters.

Republicans said Democrats should follow the rules and, if the roles were reversed, would also challenge the ballots.

MacArthur, the former mayor of Randolph, Morris County, and Belgard, a Burlington County freeholder, are running to replace retiring Republican Rep. Jon Runyan. The ballots being challenged also covered the U.S. Senate race and local elections in the Third Congressional District, which covers much of Burlington and Ocean Counties. It has 491,000 registered voters.

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Staff writer Jonathan Tamari contributed to this article.