Secretary of State Jennifer Brunner said Tuesday that the practice known as "sleepovers" is an unacceptable security risk.
Many local election officials have argued that the custom makes it easier to transport machines to polling sites.
Otherwise, they would have to hire moving companies to distribute the machines at a cost of thousands of dollars, something they don't have in their budgets.
Brunner says federal money will reimburse counties for the added cost.
Sleepovers are prevalent in Ohio counties that use touch-screen voting machines and are sometimes used in counties with machines that scan paper ballots.
This is the latest decision by the state's chief election official regarding controversial electronic voting machines which she had criticized and gone to court for.
Earlier this month, Brunner sued Premier Election Solutions (formerly known as Diebold Election Systems), accusing the voting machine manufacturer of breach of warranty, fraud, and not fulfilling its contracts, after hundreds of votes in several Ohio counties were "dropped" during March's primary. Those votes were discovered after the fact and reinserted into vote tabulations.
In May Premier claimed that antivirus software and human error were responsible for the glitches, and recommended counties disable the anti-virus software on the tabulating machines. That would have counteracted the state's certification process.
Last December Brunner called for the state to scrap its $21 million electronic touch-screen machines over security concerns.
Brunner this week has also reminded county election boards that, under Ohio law, voters who register within a certain time frame prior to Election Day can be immediately issued an absentee ballot without a reason.
The "no-fault absentee" voting law, passed by a Republican legislature and signed by a Republican governor three years ago, could be used to tap into college campuses, banking thousands of votes in the Sept. 30 to Oct. 6 window. That would benefit Sen. Barack Obama, who enjoys a 2-to-1 lead over Sen. John McCain among 18- to 34-year-olds, according to a Washington Post-ABC News poll released last month.
"This is one of many ways we'll be encouraging our supporters to skip the lines on Election Day and make sure their vote is cast early," said Isaac Baker, an Obama spokesman.
Of the more than 470,000 students enrolled in Ohio's public colleges and universities in 2006, the most recent figures available, nine out of 10 were Ohio residents, the state Board of Regents said. To register to vote in Ohio, a person must be a resident of the state for at least 30 days immediately before an election.
Ohio elections officials say they are working out potential kinks, such as questions about whether a vote counts when it is cast or when it's counted. They also are trying to address potential fears of massive voting fraud, and what effect this influx is going to mean on vote security.
Brunner said absentee ballots are verified once they are cast, and counted after polls close Election Day.
Allowing voters to cast their ballots weeks before Election Day is a growing trend. More than a dozen states permit early voting, and more than two dozen provide an absentee ballot to any registered voter for any reason. The battleground states of Colorado, Florida, Nevada and New Mexico allow voters both options.
In Ohio, Republicans are clearly not pleased with same-day registration and voting and have not ruled out a lawsuit against Brunner's office.
"You have to wonder, when they look at what they consider a loophole with such excitement," said Jason Mauk, the Ohio Republican Party's executive director. "That would suggest manipulating the process, and I think opens the door to suspicion."
The voting window, so far, is only being implemented in some counties - typically, urban areas or those with college campuses - leading Republicans to cry foul.
"The prospect of someone coming in with no ID and registering and voting is contrary to every sort of protection that legislators and lawmakers have built into this system for decades," said Kevin DeWine, a Republican lawmaker who is poised to take over the state party after the election. "The processes and the law and the systems in our 88 counties are not equipped to handle same-day registration."
People in Ohio can register without identification, but they have to show some sort of ID to vote.