Senate leaders are preparing for a contentious Tuesday session that could stretch several hours and could send the chamber into a closed session as Democrats try to force the GOP into accepting witness testimony and documents to be produced during the trial, according to multiple senators and other sources familiar with the planning.
Democrats will try to amend the organizing resolution that will be offered by Senate Majority Leader Mitch McConnell. Under McConnell's plan, there is expected to be no guarantee that there will be witness testimony or documents produced, decisions Republicans want to punt until after opening arguments are completed on both sides and senators have a chance to ask questions.
But Democrats will attempt to change that. Senate Minority Leader Chuck Schumer is expected to offer at least one amendment to stipulate that witnesses must testify and that documents blocked so far by the White House be turned over to senators. But Democratic senators told CNN that it's possible Schumer could try to offer multiple amendments, and that could stretch debate on for several more hours.
That's because, at the moment, it's expected that there will be two hours of debate — equally divided between the two parties — for each amendment.
It's still uncertain how many amendments there would be, or precisely how Tuesday's debate would shake out because McConnell has yet to unveil his resolution publicly that will detail the procedures of the trial.
Opening arguments from the House Democratic managers would not occur until after debate over the amendments concludes and the Senate resolution is adopted. GOP senators are expected to unify and reject the Democratic amendments.
Here's where things could also get interesting: Senators are not allowed to debate in open session while the trial is ongoing. If they want to debate, they would have to go into closed session, and a vote of at least 51 senators is required to make the proceedings private.
Otherwise, the amendments would be debated in public between the House impeachment managers and President Trump's defense team.
Schumer on Thursday suggested he would seek to limit the number of closed sessions that would occur.
A Senate leadership aide said that closed-sessions might be needed since senators are required to keep quiet during an impeachment trial.
CNN's Phil Mattingly and Ted Barrett contributed to report.