“We are pretty pissed off about it,” says one confidant. “She messed up, making it harder for other candidates to speak up. Taking on Perry on this front, with serious arguments, could have been a long and very successful line of attack. She went a step too far and embarrassed the field. She polluted the issue.”

Paul aides note that the congressman, a physician, is concerned about vaccines, but would never take Bachmann’s approach in examining the issue. “He is very cautious about vaccines, especially federal mandates. But he is ultimately pro-science,” the source continues.