red herring

red herring

phase.  something that misleads and distracts from the main subject

"Racism was not a factor in the case – that was a red herring thrown in by the defense lawyers."

"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."

origin:  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.