More than 200,000 registered Ohio voters may be blocked from casting regular ballots on Election Day because of a federal appeals court decision on Tuesday requiring the disclosure of lists of voters whose names did not match those on government databases, state election officials and voting experts said.

The court decision requires Jennifer Brunner, the Ohio secretary of state, to provide the names to local election officials by Friday. Once the local officials have the names, they may require these voters to cast provisional ballots rather than regular ones, and they may ask partisan poll workers to challenge these voters on Election Day. Both possibilities could cause widespread problems when the voters show up at the polls.

Concerns about those problems led the Ohio Attorney General’s Office to file an appeal of the decision to the United States Supreme Court on behalf of Ms. Brunner on Wednesday night.

The state’s appeal went directly to Justice John Paul Stevens because he oversees the Sixth Circuit. It argued that the Republican Party had nearly two years to raise complaints about the process of screening voter registrations and failed to do so. Any changes now to the process would disrupt preparations for the election, it contended.