The drama began after Mrs. Obama stopped off at the Martin Luther King Center on the south side of Chicago to cast an early vote.
After finishing at the machine, Obama went back to the desk and handed in her voting key.
She let voters including electrician Dennis Campbell, 56, take some photos.
"She was telling me how important it was to vote to keep her husband's agenda going," Campbell said.
According to a pool reporter from the CHICAGO SUN-TIMES at the scene, the conversation took place INSIDE the voting center, not far from the booths."