bracing for impact. >> it is very bad for our country. >> reporter: tonight sources telling cnn president trump has spent the last several days discussing mueller's upcoming appearance and he seems more irritated than anxious that he has to watch the man who has loomed over his presidency take center stage. >> i saw mueller testify -- again, how many times. two and a half years -- >> reporter: trump has been quizzing people about what to expect. while complaining that democrats will never let the investigation go. >> they think this is helping them. >> reporter: his republican allies are assuring him it won't change a thing. >> i've heard all i need to hear from mueller. >> reporter: but even if mueller reveals nothing new, sources say trump wants to expose the investigation as the hoax he believes it is. >> actually, it started practically from the time i came down on the escalator. >> reporter: trump tweeting that republicans should turn the tables by asking why were all of clinton's people given immunity and the text messages of peter