WASHINGTON (CNN) - Democratic presidential candidate Barack Obama said Wednesday he is frustrated over the circulation of an e-mail that claims the Illinois senator refused to place his hand on his heart during the Pledge of Allegiance.
"This is so irritating," Obama said in response to a question about the claim at a town-hall event in Burlington, Iowa. "My grandfather taught me how to say the Pledge of Allegiance when I was one or two."
The e-mail in question shows a photo of Obama, as well as rival candidates Sen. Hillary Clinton and New Mexico Gov. Bill Richardson during Iowa Sen. Tom Harkin's steak fry in September. Harkin's wife, Ruth, is also pictured. Richardson, Clinton, and Harkin all have their right hands on their heart while Obama's hands are at his sides.
The e-mail goes on to say Obama "refused to not only put his hand on his heart during the Pledge of Allegiance, but refused to say the pledge."
Obama told the questioner the picture was actually taken during a playing of the national anthem and said, "During the Pledge of Allegiance you put your hand over your heart, during the National Anthem you sing."
"This is the classic dirty trick of the campaign," Obama said later Wednesday at an event in Cedar Rapids.
Related video: Watch Sen. Obama respond to the e-mail accusation.
– CNN's Dugald McConnell contributed to this report