Some scholars and voting-rights activists sounded the alarm today about changes in Ohio’s voting system suggested last week by Ohio’s secretary of state, Jennifer L. Brunner. The secretary, a Democrat, proposed replacing all of the state’s voting machines with optical-scan machines, consolidating small polling places, eliminating vote counting at precincts in favor of a central location, and moving to a vote-by-mail system for special elections.

Ms. Brunner made the recommendations after receiving a report from computer scientists that said the state’s voting machines could easily be hacked and votes stolen.

Lawrence Norden, chairman of the Brennan Center Task Force on Voting System Security at the New York University School of Law, said the proposed changes could disfranchise tens of thousands of voters, particularly the elderly, the poor, and members of minority groups. Sometimes those voters choose multiple candidates for a given race, disqualifying their ballots. If their ballots are scanned at precincts or they vote on touchscreen machines, voters are able to recast their votes, he said. In the 2004 presidential race about one million voters were given an opportunity to recast their votes after accidentally “overvoting” at precincts, he said.

He said Ms. Brunner’s plan for counting votes at a central location would introduce the possibility of voter fraud on a huge scale. It’s better if election workers detect software glitches or malfeasance at individual precincts, he said.

In addition, he said, eliminating smaller precincts could harm voters who can’t travel to faraway voting centers because they don’t have cars or access to public transportation. —Andrea L. Foster