In the state that is likely to decide the leader of the free world Tuesday, an 11th hour "experimental software patch" is causing consternation, confusion and a lawsuit.

Ohio, regarded as the "tipping point" swing state in Governor Mitt Romney and U.S. President Barack Obama's quest for 270 electoral votes Tuesday, uses electronic voting machines. A large portion are provided by ES&S, the nation’s largest e-voting system manufacturer.

Late last week, a leaked work order revealed that John Husted, Ohio's secretary of state, had installed something called EXP on central tabulation machines in 39 of Ohio's 88 counties. EXP is either an "experimental software patch", according to the company's work request to ES&S, or, as the Secretary of State's office has called it, a "reporting tool".

Now Husted finds himself caught in Election Day drama. A rival Ohio politician has filed suit, prompting a judge to rule whether those "patched" machines can legitimately be used in the vote count at 9 a.m. on Election Day.

The EXP update will allow election officials to "output election results on a thumb drive, and upload [them] at once into the Secretary of State’s system," Matt McClellan, a spokesman for the Secretary of State told a local news site called TheGrio.

The ES&S contract [PDF], however, says nothing about thumb drives.

EXP, XML, CSV?

The only purpose of EXP mentioned in the work order is simply this: to convert XML files into CSV files, so Husted's computers can read the numbers and upload them to the web immediately.

But as voting machine security expert James March testified in an affadavit, that's a strange thing to install on tabulation machines. You could just convert the files on the secretary's computer. Why bother installing this patch, or tool, on 39 machines?

“What ES&S has chosen to do here is extremely dangerous and exactly what you’d want to do if you wanted to plant a cheat onto the central tabulator,” March says. "Deliberate tampering of that data using uncertified, untested software would be child's play."

After refusing multiple media requests, McClellan spoke to the Christian Science Monitor late Monday evening.

Calling the politician's case a "ridiculous lawsuit," he said the Secretary of State's office had cleared this EXP work order by the appropriate Federal agency. "We've not made any software patch, update or change to the tabulation system these counties are using. We haven't touched them."

XML, CSV, security experts: what could be going on here, if anything? Let us know in the comments.