Kinzinger, a member of the National Republican Congressional Committee's Young Guns program, takes issue with people questioning his service record.
"I know where I've served and I know what I've done," Kinzinger said.
The NRCC backed up their candidate.
"Are things so bad for the Democratic Party that they have to attack a distinguished member of the military like Adam Kinzinger just to keep their heads above the water?," Tom Erickson, an NRCC spokesman, said in a statement. "This is nothing but a shameless political attack by a party desperately trying to change the subject from their gross mishandeling of the economic crisis."
Democratic operatives, meanwhile, pointed to a change in his website's biography page as a sign he had overstated his military record. The 31-year-old former McLean County Board member has made his military service a central theme of his campaign.
First, the bio on his website read: "In 2003, Adam joined the United States Air Force. He was commissioned a 2nd Lieutenant in November 2003 and was awarded his pilot's wings in 2005. Captain Kinzinger now serves as a pilot with the Air Force Special Operations Command."
The last sentence was later changed to "Captain Kinzinger has served in the Air Force Special Ops, Air Combat Command, Air Mobility Command, and Air National Guard."
Kinzinger said the changes to his online biography were designed to clear up the misconception about his piloting experience.
"We added basically all my past commands to the bio," he said. "That was my effort to go into even more depth."
Kinzinger said he's tried getting in touch with the individuals who contacted him about his service record but added he won't back away from showcasing his time in the Air Force. "It's authored into who I am."
Updated at 8:45 p.m.