As he filled out a form for his vote, he asked one worker: "What`s my date of birth? 8/4/81?".
The worker quickly replied: "Nice try."
"I was just shaving a couple of decades off," Mr Obama said.
Mr Obama has been encouraging people in speeches and radio interviews to register to vote and to get to the polls. He led by example on Friday.
He shook the hands of about a dozen poll workers and was directed to a desk where cameras watched from about 30 feet away.
As Mr Obama marked the ballot, he joked about the camera operators catching his every move. He said: "Now, they can`t see me, can they?"
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