Update 1/31 2:53 p.m. ET: When Republican Sen. Lisa Murkowski said she opposes new witnesses Friday afternoon, Democrats' hopes of calling any new witnesses went up in flames.

After two long weeks, the conclusion of President Trump’s impeachment trial — and the legacy it portends — now appears to rest with just one man: Chief Justice John Roberts.

After the Senate wrapped up its 16-hour question period that stretched over two days, Sen. Lamar Alexander (R-Tenn.) released a bombshell of a statement Thursday night: “There is no need for more evidence.”

Alexander was widely viewed as the potential fourth vote Democrats could get to reach the magic 51 votes they’d need to override Senate Majority Leader Mitch McConnell’s blockade on allowing any new evidence into the proceedings.

So now the count is 50-50, assuming GOP Sens. Susan Collins, Mitt Romney, and Lisa Murkowski side with Democrats to subpoena former National Security Advisor John Bolton to testify. And while every senator can change their mind up until voting has been gaveled to a close, it very much looks like the Democrats' only hope to bring in witnesses lies with Roberts, who''s been presiding over the trial and could step in to break the tie.

That prospect has left senators gaming out what, exactly, Roberts believes and how he’s likely to rule.

The chief justice is famously respectful of existing precedent, and some Democrats hope that will guide Roberts’ thinking on whether this impeachment trial should be the first to be conducted without witnesses. Former Chief Justice Salmon Chase cast two deciding votes in then-President Andrew Johnson’s impeachment trial in the 1800s.

“The history is clear. All you’ve got to do is go back and read the history,” said Sen. Patrick Leahy (D-Vt.), former chair of the Judiciary Committee. “Knowing Chief Justice Roberts as well as I do, and I've known him for years, he's read the history more than any of us.”

Others aren’t so sure, including Sen. Josh Hawley (R-Mo.), who clerked for Roberts before joining the Senate.

“Just based on what I know of the chief justice, he is someone who is usually – he's very cautious on the law,” Hawley told VICE News in the basement of the Capitol. “I don't know, but I would guess he would probably, whatever the question, if it’s 50/50, I bet he doesn't decide it… if it's not settled ground and it's controversial, I think he would not want to break new ground. But I could, again, I could be wrong.”

This comes the same week as transcripts of Bolton’s forthcoming book surfaced where he alleges Trump explicitly tied Ukraine military aid to an investigation of former Vice President Joe Biden and his son Hunter, which is why most Democrats are furious about the prospect of setting a new precedent of holding a presidential impeachment trial without witnesses.

Republicans feel like McConnell has won the most high-stakes fight of his decades-long political career.

“I'm in the room, and I'm getting more optimistic,” Sen. Lindsey Graham (R-S.C.), the chair of the Judiciary Committee, told reporters about his hunch that McConnell has the votes to end the trial by Saturday. “He's pretty good at what he does, and I've been in the room where people are beginning to consolidate around the idea [of blocking witnesses].”

There’s still fear among Democrats that three moderates in their party — Sens. Joe Manchin of West Virginia, Doug Jones of Alabama, and Kyrsten Sinema of Arizona — may break ranks and vote to acquit Trump on at least one of the two articles of impeachment, though Democrats are confident they’ll vote to hear from at least John Bolton.

Still, even these moderates' Democratic colleagues say they’re largely in the dark as to what they’re thinking, because they’re forbidden from talking to other senators during the trial.

“I think that it’s likely to be Republican members who make the ultimate decision of whether we're going to have a full and fair trial,” Sen. Tammy Baldwin (D-Wis.) told VICE News while waiting for a tram under the Capitol.

The thought of relying on Roberts to side with Democrats has some in the party downcast.

“If there's a tie vote, the likelihood of the chief justice breaking the tie is very slim,” Sen. Richard Blumenthal (D-Conn.) told VICE News, before arguing the GOP will be punished if they close down these historic proceedings without allowing one of the most important parts of any trial.

“On one hand, they say it's all hearsay – there's not enough information. But they refuse to see more information or evidence,” Blumenthal said. “They can't have it both ways. If they put blinders on, they can’t complain about what they can't see. And they’re putting blinders on.”

“I'm incredulous that everybody doesn't want witnesses,” Sen. Sherrod Brown (D-Ohio) told VICE News at the Capitol. “Trump has been saying for a year, ‘All hearsay. All hearsay.’ Well, let's have somebody that was in the room there.”

Brown says this isn’t about justice but merely politics. He argues it’s in line with McConnell’s decision to turn some cameras off in the chamber this week so people couldn’t see senators asking their questions, while also restricting reporters' access to senators in parts of the Capitol throughout the trial.

“McConnell wants this over as quickly as possible with as little media coverage as possible. This is a sham trial,” Brown said. “I mean, if he doesn't want the media coverage, he doesn't want it to last very long, and he's not allowing witnesses means the public again is going to see that this is a rigged system.”