The I-Team looked into this after receiving calls about how authorities ensure somebody doesn't vote early in one location and then drive across town to another.
Real-time security is in place in Chicago and Cook County to make sure early voters cannot vote twice.
An electronic database records the name of every early voter -- a database available in all early voting precincts and cross-checked every time somebody comes in to vote.
So far, the records are bulging. In Chicago, 16,000 on Thursday alone push the four-day total to more than 64,000 early voters -- 40 percent more than four years ago.
In suburban Cook County, more than 58,000 are voting early -- almost a 50-percent increase.
When President Obama voted early Thursday in Chicago, he had to sign over and surrender the absentee ballot he was mailed-to prove that he hadn't already voted.
Similarly, if the president -- or any other early voter -- showed up at their Illinois polling place on Election Day, they wouldn't be allowed to vote again.
At the beginning of the day November 6th, election judges are provided lists of early voters and then place a sticker or other marking over a voter's name on the registration record, showing that person already voted.
If there are questions about whether someone has already voted, they are allowed to vote what is called a provisional ballot that isn't counted on election night but is set aside and investigated after the polls close. It can always be added to the total if it is determined to be legitimate. The aim here is: one person, one vote.