dig for dirt (on someone or something)

To search for scandalous or damaging information about someone or something. I'll ask my usual sources at the tabloids to start digging for dirt on that actress. She can’t treat you like that and get away with it. The politician's lawyer has been digging for dirt, but so far he hasn't found anything to tarnish their opponent's campaign. I've been digging for dirt on my enemy but have been unsuccessful so far.