get the dirt on (someone)

To obtain scandalous, incriminating, or otherwise damaging information about someone. A: "I don't know, I don't feel right snooping around his personal life like that." B: "Hey, you're an investigative reporter. Getting the dirt on people is your job!" Tabloids are always eager to get the dirt on famous celebrities. No, I don't want anyone to get the dirt on the opposition. I'm running a clean campaign here.