Ron Paul was booed at the 2012 Republican debate when he said Iran didn't have a weapon (they didn't).

He then made my favorite statement of the debate:

"Now, if they're so determined to go to war, the only thing I plead with you for if this is the case, is do it properly. Ask the people and ask the Congress for a declaration of war. This is war! People are gonna die and you gotta get a declaration of war!"