(AP) COLUMBUS, Ohio - Provisional ballots must be counted in a tight congressional race in central Ohio, one of the last undecided contests in the nation, a federal judge ruled Thursday.

The decision by U.S. District Judge Algenon Marbley could affect the outcome of the race between Republican Steve Stivers and Democrat Mary Jo Kilroy in the 15th District. But his ruling was immediately appealed, and provisional-vote counting was put on hold for another week.

Stivers’ lead grew to 479 votes over Kilroy on Thursday, after one county finished its official count. The two are running to succeed retiring Republican Deborah Pryce, who only narrowly beat Kilroy in 2006.

The case before Marbley involved ballots cast in Franklin County, the largest and most Democratic-leaning in the district.

"This case touches on the most fundamental of rights of American citizens: the right to vote," Marbley said.

Provisional ballots are issued at polls to people who believe they have been wrongly denied the right to vote. About 1,000 ballots are in dispute in the House race because of defects such as voters failing to both print and sign their names.

Marbley’s ruling came in a lawsuit filed last week by supporters of Stivers, who argued the ballots were invalid because they were missing either a printed name or a signature, or the two were interchanged on ballot envelopes.

In his ruling, the judge said that the plaintiffs never disputed that voters who used the provisional ballots were eligible, properly registered and voted in the correct precinct, and that not counting the ballots would disenfranchise legitimate voters.

His ruling sides with Secretary of State Jennifer Brunner, who had said the ballots should be counted because the problems were due to poll worker error.

Punctuating his ruling with a reading of Ohio’s voter fraud statute, Marbley called unfounded the plaintiffs’ contention that allowing the disputed ballots to be counted would promote fraud. He said election officials have ways to double-check the validity of all the disputed votes.

The plaintiffs filed their appeal Thursday with the 6th U.S. Circuit Court of Appeals in Cincinnati within minutes of Marbley’s ruling, and he granted an injunction to prevent ballots from bring counted until 9 a.m. Nov. 28.

Though the lawsuit pertains to only about 1,000 questioned ballots in the House race, it affects the counting of all 27,306 of the county’s outstanding provisional ballots. That is because no provisional ballot can be counted until the rules are determined for them all.

In addition to the U.S. House race, the uncounted ballots could play a role in two state House races. The Ohio vote is one of three U.S. House races still up in the air nationwide.