To understand why Coleman suspects some 150 people got two votes during the Senate recount, you need to know a little bit about how Minnesota processes absentee ballots.
Unlike normal ballots, absentees come all folded up. Poll workers have to unfold the ballots and then feed them into vote counting machines. And if you've ever tried to feed a wrinkled old dollar bill into a vending machine, you can guess what the problem is.
Just like vending machines, vote counting machines have a hard time reading paper that's wrinkled or creased. So election judges have to make a duplicate ballot to feed into the machine.
"You have two judges of separate parties. They sit down. You look at the original ballot. You take a blank one to duplicate it. You color in the ovals. And then the two of you look at it and agree you made an accurate copy," said election judge Brent Harring, who was in charge of Minneapolis ward 10, precinct 2.
"Then there's the part where you label them 'original number 1,' etc. [and label] the duplicate, 'duplicate number 1,' etc.,'" Harring concluded.
But Coleman's lawyers believe that in 22 precincts, including Harring's, judges forgot that final step; they didn't label and number the duplicates.
If Coleman is right, then those ballots would have been double-counted during the recount -- first as originals and again as duplicates. And many election judges, including Harring, say they can't remember for sure whether all the ballots were labeled correctly or not.
"I don't recall that [labeling the duplicates] was part of the process," said Emily Manhart, an election judge who made two duplicate ballot in Minneapolis ward 7, precinct 7. But Manhart added quickly, "that doesn't mean that it didn't get done.'"
Gina Letts, who duplicated a larger stack of ballots in that precinct, says she is "about 75 percent sure" she labeled her ballots correctly.
Almost all the election judges Minnesota Public Radio News contacted had a hard time remembering exactly what happened that night. This was a small detail. It seemed insignificant at the time, and it came at the end of a hectic day more than two months ago. That will be an obstacle for Coleman, who has the burden to prove the double counting happened.
Democrat Al Franken's lawyers say there are other plausible explanations for the discrepancies between the numbers of duplicate and original ballots in certain precincts. One possibility is that some ballots that needed to be duplicated weren't. Another is that the duplicates were made, but were never fed into the machine. That is what appears to have happened in Minneapolis ward 8, precinct 7.
"We all thought we were all done, and I called out across the room, 'Do we have all the ballots?'" Assistant Chair Election Judge Nancy Birth recalled. "And everybody said, 'Yes, you have all the ballots,' and I said, 'OK. I'm going to close the polls.'"
They turned off the voting machine, printed out their vote totals, and started packing up the equipment. And that's when they discovered a small stack of ballots that hadn't been counted.
"And we all went 'Oh no! Now what do we do?' because we realized they should have been run through the machine but they weren't," Birth said.
There were a dozen ballots -- mostly duplicates -- but it was too late to count them. The election judges wrote a note explaining what had happened and delivered the ballots to city election officials with the rest of their elections materials. But the ballots were apparently misplaced again, and weren't discovered until after Minneapolis completed its recount. That means they couldn't have been double-counted.
But just because Coleman appears to be wrong about that precinct, doesn't mean he's wrong about the others. The recount did produce more votes in those precincts than the number of voters the election judges reported had voted there.
If the three-judge panel presiding over the election contest rules that Coleman is right about the duplicate ballot issue, it may spark a wider inquiry. Franken's campaign has already requested information on a number of precincts in Coleman-friendly Anoka county.
Anoka also had discrepancies related to duplicate ballots, and Franken's side believes Coleman may have gotten more votes there than he deserved.