what does it require? when speaker pelosi formally gavelled in these house votes, it was a constitutional requirement for the senate. begin a trial of the president, and there is no debate about that requirement. >> well, under the senate rules we're required to take it up if the house does go down that path, and we'll follow the senate rules. >> trial of donald trump will define him in history and provide a frame work for americans to assess evidence of his conduct heading into this campaign. no other president has ever run for office after impeachment because no other president got themselves impeached this quickly. so this matters, and the battling has already begun over how to run the trial. senate leaders jousting over these past examples. but there are very few precedence because there's only been, as you have heard by now, two presidential trials in all of history. so right now we turn to one of the most momentum special reports we have done here, what do the rules require when the president is put on trial and