Susan Davis reports on the president’s address on health care.

Associated Press South Carolina Republican Rep. Joe Wilson.

President Barack Obama’s address to Congress this evening was moving along fairly smoothly until he pledged that there was nothing in the legislation that would provide health care to the millions of illegal immigrants residing in the nation.

A cry of “You lie!” was audible from the Republican side of the aisle. That heckler was South Carolina Republican Rep. Joe Wilson. (Watch the video HERE.)

“It’s not true,” the president responded to the outburst, while House Speaker Nancy Pelosi, seated behind the president, offered her mother-of-five glare towards the Republican side of the chamber. First Lady Michelle Obama was seen shaking her head from side to side.

While lawmakers may have become accustomed to that kind of language during the contentious town hall meetings in August, Wilson’s outburst was uncommon for a joint session of Congress, where decorum usually reigns.

A spokesman for Wilson did not immediately return a request for comment.

UPDATE: Wilson’s comment has prompted immediate and intense reactions. “Joe Wilson” is currently the number one search item on Twitter, and fellow Republican and Arizona Sen. John McCain called his comment “totally disrespectful” on CNN’s Larry King Live. McCain said Wilson should apologize to the president “immediately.” Missouri Democratic Sen. Claire McCaskill weighed in on her Twitter page: “Biggest disappointmnt (sic) of evening, the total lack of respect shown by one member for the President.Never acceptable to behave like a jerk.”

UPDATE 10:33 p.m.: Wilson apologizes in a statement: “This evening I let my emotions get the best of me when listening to the president’s remarks regarding the coverage of illegal immigrants in the health care bill. While I disagree with the president’s statement, my comments were inappropriate and regrettable. I extend sincere apologies to the president for this lack of civility.”