Tonight on the Last Word: Alexander Butterfield’s surprise testimony led to President Nixon’s resignation. Also, a judge denies Steve Bannon’s request to delay his contempt of Congress trial in the Jan. 6 probe. Plus, Uvalde families march to demand answers from officials. And a Texas newspaper details police inaction in a 77-minute Robb Elementary School surveillance video. Alexander Butterfield, Jill Wine-Banks, Andrew Weissman, Jazmin Cazares, Texas State Sen. Roland Gutierrez and Tony Plohetski join Lawrence O’Donnell.