The Georgia State Election Board voted on Friday to force counties to hand-count all ballots cast on Election Day, a move critics say could significantly delay the reporting of results in the battleground state and inject chaos into the post-election period.

The new rule, which passed on a 3-2 vote, runs counter to extensive legal advice from the top election official and law enforcement officials in the state. A nonpartisan collective of local election officials had also objected to the change.

The new rule is the latest in a stream of right-wing election policies passed by the State Election Board over the past few months. The board has come under increasing pressure from critics already concerned that it has been rewriting the rules of the game in a key swing state to favor former President Donald J. Trump. Last month, the board granted local officials new power over certifying the election, which opponents say could potentially disrupt the process if Mr. Trump loses in November.

The new rule to require hand counting in addition to a machine count, critics argue, could introduce errors and confusion into the process and potentially disrupt the custody of ballots.

To start hand-counting on election night, poll workers would likely have to break open the seals on boxes of completed ballots, possibly exposing the ballots to fraud or loss. In previous elections, ballots remain sealed and stored securely unless a recount was ordered.

The hand-counting rule was among nearly a dozen election changes under consideration on Friday. The proposals included a variety of conservative policy goals like expanding access for partisan poll watchers. The proposals come just 46 days before the election, after poll workers have been trained and ballots have been mailed to overseas voters.