(The precedent that's useful to him here is, all previous presidential impeachments have been based on violating federal laws.)
(Seems to mean he will not start the Senate trial without Pelosi sending the articles over, as some experts suggested he can. But not done talking yet.)
(Again, he doesn't mean that pressuring a foreign government to investigate your domestic political rival is unprecedented.)
"The Senate’s duty is clear. When the time comes, we must fulfill it."