Impeach him for what? She hasn't given a real reason.
It was mentioned above "unless they know something we don't", but I find that highly unlikely as the media would have been all over anything like that.
IMO, this is an act of desperation. The Dems are in trouble and they know it. Word has it that Biden will soon be ending his campaign, and who does that leave? The only two current candidates who have a chance are Pocahontas and Buttidude, and neither are really doing well.
I seriously think that short of an October surprise, we're looking at a Trump landslide. Not so much because of Trump, but because the Dems have turned off so many voters.