After an opening salvo of back-and-forth arguments from President Trump's attorneys and Democrats' impeachment managers on Monday, Senate impeachment trial proceedings are set to begin at 1 p.m. on Tuesday with the expectation they will stretch well into a wild night on Capitol Hill -- even as key procedural questions, including the timeline for debate and whether additional witnesses will testify, remain undecided and hotly contentious
In a surprise move Monday night, a detachment of high-profile House Republicans announced that they would formally join the president's legal team, including Reps. Doug Collins, Mike Johnson, Jim Jordan, Debbie Lesko, Mark Meadows, John Ratcliffe, Elise Stefanik, and Lee Zeldin.
The last-minute show of force underscored the fluid nature of the Senate trial, which is also set to feature full-throated arguments against impeachment from constitutional scholar Alan Dershowitz and Bill Clinton independent counsel Ken Starr.

Democrats have seethed openly ever since House Speaker Nancy Pelosi, D-Calif., failed in her gambit to force Senate Majority Leader Mitch McConnell's hand before the House would turn over the articles of impeachment to the Senate. Pelosi had sought a commitment allowing Democrats to call witnesses prior to arguments in the trial.
McConnell specifically revealed Monday that he wanted a condensed, two-day calendar for each side to give opening statements, at 12 hours per day. After the four days of opening arguments, senators would be allowed up to 16 hours for written questions to the prosecution and defense, followed by four hours of debate. Only then would there be votes on calling other witnesses, likely next week. At the end of deliberations, the Senate would then vote on each impeachment article.