Before the Senate can deliver a verdict on whether to oust Trump from office, the “world’s greatest deliberative body” must first set ground rules on the president’s impeachment trial. At issue is what kind of amendments or witnesses to consider, as well as how long the proceedings will go on and what kind of evidence can be introduced, all of which will shape the trial and its fallout.

It’s a process fraught with uncertainty and political peril, particularly with an impeachment trial to come right in the heat of a Democratic presidential primary in which six senators are running to defeat Trump.

Whether the Senate can show some semblance of unity before plunging into what’s sure to be a deeply acrimonious trial will depend on McConnell and Schumer and their ability to keep their caucuses in line.

“There’s no reason we can’t come up with an agreement. .… I’m open to trying to be fair and down the middle and letting the facts come out and be nonpartisan,” Schumer said in an interview on Wednesday. “There’s no reason we can’t come up with good, fair and honest rules.”

“I would think there would be collective interest in trying to get this done in a reasonable time,” said Sen. John Cornyn (R-Texas), a close adviser to McConnell. “I don’t think Bernie Sanders or Elizabeth Warren will object to trying to have a limited time frame to hear the case and to make a decision.”

Some senators are hoping the body can replay the comity it displayed during the opening phases of then-President Bill Clinton’s 1999 impeachment trial.

"There’s no reason we can’t come up with good, fair and honest rules." Senate Minority Leader Chuck Schumer

Sen. Patrick Leahy (D-Vt.) has quietly met with McConnell and Schumer to ask for a senators-only meeting — similar to the famous session that occurred in the Old Senate Chamber on Jan. 8, 1999 — to hash out a deal on how to proceed with a Trump trial, if it comes to that. The 1999 impeachment rules package, crafted by then-Sens. Ted Kennedy (D-Mass.) and Phil Gramm (R-Texas), passed on a 100-0 vote, which was hailed by senators as a momentous achievement, yet seems nearly impossible to imagine occurring in today’s Senate.

“I talked to the appropriate people,” Leahy said, reprising the role he played more than 20 years ago in trying to bring his colleagues together. “The worst thing that could happen to this body — which is important to this country — is we engage in political gamesmanship.”

McConnell (R-Ky.) declined to comment for this story but said this week that he and Schumer (D-N.Y.) have not discussed the matter.

Yet McConnell added that — given the evidence today — he doesn’t “think there’s any question” the Senate will acquit Trump, a powerful message to the Republican rank-and-file senators he’s led for the past 12 years.

Senators and aides in both parties said the lack of interaction between McConnell and Schumer on this topic is no reason for alarm given that the House has not yet compiled its articles of impeachment. Yet the sense of urgency could be growing, with the House inquiry moving to public hearings next week.

The White House, for its part, has already started quietly plotting out its strategy for a Senate impeachment trial. White House counsel Pat Cipollone has begun reaching out to Senate Republicans to discuss the rules and procedures for the proceedings, according to GOP senators and aides, a sign of how seriously Trump’s legal team views what’s unfolding on Capitol Hill.

Trump reaching out to Senate Republicans as well. The president has been calling more senators directly, in addition to hosting more lunches and dinners at the White House.

But can the Senate match the bipartisanship that then-Majority Leader Trent Lott (R-Miss.) and Minority Leader Tom Daschle (D-S.D.) demonstrated as the Clinton trial got underway — the famous 100-0 vote?

“Do I think that will happen this time? I hope so, but I doubt it,” Sen. John Kennedy (R-La.) said. “You’re going to see Republicans line up on one side and Democrats on the other. I hope I’m wrong, but I don’t think we’ll even be able to get agreement on the rules.”

“You’d like to think it could [be unanimous]. And it definitely should. But we’ve never been in times like this,” Sen. Joe Manchin (D-W.Va.) said.

Despite the glossy sheen now applied to the unanimous 1999 vote, the debate over how to conduct the trial was bitter. Senators passed the motion to subpoena witnesses on a nearly party-line vote, for example, and Democrats tried to amend a resolution to subpoena key witnesses, including Monica Lewinsky. And this all took place in a Senate that still operated with a modicum of regular order. The Senate today doesn’t even compare to that era in terms of being able to get things done.

The Senate is shown Jan. 8, 1999, in this image from video as senators unanimously approved a blueprint for President Bill Clinton’s impeachment trial. | AP Photo

“People have a rosy view of what happened in the past. It’s never quite as good as what you think,” Sen. Lamar Alexander (R-Tenn.) said. “I think it would be harder today, but if McConnell and Schumer sat down and agreed on something, I think most senators would agree with that.”

Though Senate leaders have not yet settled on how to craft the rules package governing the trial, under a majority vote threshold the rules proposal can be subject to amendments on the Senate floor. So a senator like Sen. Rand Paul (R-Ky.), who has been calling for Hunter Biden to appear in the Senate, could conceivably offer amendments subpoenaing witnesses. The House impeachment inquiry centers on Trump pressuring Ukraine’s president to investigate political rival Joe Biden and his son Hunter in exchange for foreign aid.

And in theory, the 53-member Republican majority could steamroll Democrats in a party-line vote, though senators said that would be a worst-case scenario.

“It doesn’t do much good to have a process, even if it’s fair, that doesn’t look fair. So I’d be careful to impose rules heavy-handedly on the minority,” said Sen. Kevin Cramer (R-N.D.), a Trump ally.

Among the issues that will have to be hashed out: How many questions a senator can submit and the option to dismiss the trial. Aides familiar with internal discussions said the mechanism to dismiss the trial will be a key point of debate, particularly because Republicans could have enough votes to dismiss the trial fairly early in the process.

For now, much of the activity on the trial has been siloed between the two caucuses.

McConnell and his leadership team have given presentations on impeachment procedure, and Republicans have been informed that Chief Justice John Roberts will assume a role similar to a trial judge, ruling on motions or referring them for votes at a simple majority.

Schumer has spoken with all of his senators running for president about the looming trial as well as Speaker Nancy Pelosi (D-Calif.), according to an aide. He’s also created a document hub of information for Senate Democrats to access and has urged Democrats to talk about pursuing legislation on ending gun violence, health care and election security while urging a thorough House investigation.

But after they navigate the coming government funding deadline on Nov. 21, Schumer, McConnell and their respective caucuses will have to come together. Despite all the barbs from Schumer that McConnell runs a “legislative graveyard” and anger from McConnell over Schumer’s filibuster of defense funding in October, there’s some hope the two leaders can avoid damaging the chamber’s reputation yet again.

“Twenty years ago, there was a feeling of historic gravity here and we needed to rise to the occasion,” Senate Minority Whip Dick Durbin (D-Ill.) said. “I’m hopeful if the House presents us with impeachment that we see a different environment in the Senate than we’ve seen for the past year.”