COLUMBUS, Ohio -- Franklin County elections officials are notifying more than 2,000 residents that they were assigned to the wrong congressional race during last month's primary.

Confusion over a district boundary led to 56 votes being wrongly cast in the special election primary for Ohio's 12

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Congressional District, board spokesman Aaron Sellers said.

Those votes will still be counted because elections officials didn't keep track of which candidate each of the 56 voted for, Sellers said.

It wasn't immediately clear how many of those 56 votes were cast in the Republican special election primary, where Troy Balderson beat Melanie Leneghan by just 664 votes.

While the error doesn't, by itself, throw the 12th District GOP primary results into doubt, it comes as Leneghan is already challenging the vote count in Muskingum County, where she claims elections officials illegally opened ballot boxes ahead of a recount.

It also slightly changes the voter population in the 12th District, which could matter if Aug. 7 special election becomes a nailbiter between the Republican and Democratic nominee Danny O'Connor (who won his primary by a wide margin).

In all, 582 Franklin County voters have been reassigned into the 12th Congressional District from the 3rd or 15th congressional districts, while 208 other voters have been reclassified out of the 12th District. That means the 12th District will see a net gain of 50 Democrats, 115 Republicans, and 210 independents.

All of these voters live near - or, in some cases, directly on - the boundary of a congressional district, which was drawn after the 2010 census. In some cases, Franklin County elections officials wrongly grouped some voters living along a district line based on their voting precinct - which sometimes didn't match up exactly with the congressional district boundary.

Other voters live in buildings that were constructed after the 2010 lines were drawn. In one case, a Westerville retirement center with 109 registered voters was built right on a congressional boundary. In accordance with election law, the entire center is now included in the 12th District, because a majority of the center's property is located in that district.

Sellers said the Franklin County Board of Elections became aware of the problem following the May 8 primary, when a Grandview Heights resident called to ask whether he was assigned to the wrong congressional district. Elections officials took about a month to launch a countywide review to find how many other voters were in the wrong congressional district.

So far, Franklin County officials have only verified voters' proper congressional districts, Sellers said. The board of elections will now launch additional reviews to ensure residents are voting in the proper legislative districts and for other local offices, he said.

"Obviously, this is not something we're excited about," Sellers said of the errors.