A logical fallacy in which an argument to prove one thing actually proves something else. If the argument is extremely long and boring, many people wouldn't notice.

Example: "You should vote for J. Random Politician! Both George "W" Bush and Al Gore are beholden to large evil corporations for campaign contributions!" Maybe so, but you haven't proven why i should vote for J. Random, just that the other two suck.

To prove the conclusion irrelevant, show that the conclusion proved is not the one stated.