Senate Minority Leader Chuck Schumer (D-N.Y.) didn’t want to discuss what Democrats would do to counter McConnell if Republicans move for a quick acquittal vote.

“You’ll hear from us. I’m not going to talk about that right now,” Schumer said Saturday afternoon after Trump’s defense team had made its opening remarks.

After the White House team concludes its presentation on Monday or Tuesday, the trial will move to its next phase: a 16-hour round of questions from senators to the House managers and the president's lawyers. If the procedure is modeled after the process used during former President Bill Clinton's 1999 impeachment trial, senators will submit written questions that will be read aloud by Chief Justice John Roberts. Each side will alternate questions.

Rep. Adam Schiff (D-Calif.), the lead House manager, said Saturday that he expects each side's questions will be vetted by their respective leaders. Senators in both parties expect they will use up the entire 16-hour time period, though Murphy said he feared McConnell would try to squeeze it into one marathon overnight session. Senators didn’t conclude a vote on the trial rules last week until almost 2 a.m. Wednesday morning.

In the 1999 Clinton trial, following the question-and-answer round, senators then heard arguments on a motion to dismiss the case, as well as a motion to seek witness testimony and admit new evidence.

In the Clinton trial, the motion to dismiss was defeated, while the motion for witnesses and evidence was adopted. The Senate debated each motion in closed session, beating back an effort by Senate Democrats to keep the proceedings public.

There were then three days of closed-door deliberations by the Senate on the Clinton impeachment articles. Clinton was acquitted on both counts.

However, there is no requirement that the Senate engage in such closed-door deliberations, either in the organizing resolution for the Trump trial or Senate rules. As long as McConnell can muster 51 votes, the majority leader can direct the proceedings in any way he chooses.

But McConnell will have to avoid alienating centrist Republicans during the endgame if the Trump proceedings end quickly. Already Sens. Susan Collins (R-Maine) and Rob Portman (R-Ohio) have pushed back against McConnell’s attempts to speed up the trial and deviate from the Clinton precedent.

Some senators may object to a final vote on Trump’s guilt or innocence without a chance to make a statement to their colleague behind closed doors. McConnell could then agree to a shorter period than used in the Clinton trial, although Schumer will likely try to drag it out.

And there are other motions that Schumer could offer following the question-and-answer period, although McConnell could counter that these motions are a stalling tactic and just designed to needlessly extend the trial. Regardless of hypotheticals, senators are preparing for the possibility that the whole thing could be over shortly after the key procedural vote next week as long as McConnell has 51 votes to do it.

“My understanding of the rules is that he left that door open, should he choose, to do exactly that,” said Sen. Martin Heinrich (D-N.M.).

Kyle Cheney contributed to this report.