red herring

Something irrelevant that diverts attention away from the main problem or issue. The candidate used the minor issue as a red herring to distract voters from the corruption accusations against him. The mystery writer is known for introducing red herrings to arouse the reader's suspicion of innocent characters.

a piece of information or suggestion introduced to draw attention away from the real facts of a situation. (A red herring is a type of strong-smelling smoked fish that was once drawn across the trail of a scent to mislead hunting dogs and put them off the scent.) The detectives were following a red herring, but they're on the right track now. The mystery novel has a couple of red herrings that keep readers off guard.

Something that draws attention away from the central issue, as in Talking about the new plant is a red herring to keep us from learning about downsizing plans . The herring in this expression is red and strong-smelling from being preserved by smoking. The idiom alludes to dragging a smoked herring across a trail to cover up the scent and throw off tracking dogs. [Late 1800s]

A misleading clue. Many people who know the phrase believe it came from the practice of game poachers laying scents of smoked herring (smoking accounted for the fish's reddish color) to throw gamekeepers and their dogs off the poachers' scent. However, etymologists discount that explanation, favoring instead that the phrase originated with an English writer who used the scent-laying image as a metaphor for a particular political plan. Mystery writers, readers, and critics use “red herring” to describe a piece of plotting intended to throw the reader off in deducing who-done-it. The financial world uses the phrase to mean a stock prospectus, not from any intent to deceive, but because the document has a red cover.