(AP) — Donald Trump’s historic second impeachment trial is an undertaking like no other in U.S. history. Proceedings begin Tuesday in the Senate with the defeated former president charged by the House with inciting the violent mob attack on the U.S. Capitol to overturn the election. Prosecutors argue it is a “grievous constitutional crime,” but Trump’s defense team insists his fiery words are just a figure of speech and, besides, trying a former president is unconstitutional. The debate over that constitutional question is expected to highlight the opening day. White House press secretary Jen Psaki says President Joe Biden will be busy with the business of the presidency and won’t spend much time watching the proceedings.