Republicans are signaling confidence that Chief Justice John Roberts will not insert himself into the middle of the looming fight over witnesses at President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE’s impeachment trial.

GOP senators are cautiously optimistic they will be able to fend off any effort to call new witnesses. But with several of their colleagues still undecided ahead of Friday’s vote, the possibility of a 50-50 tie is seen as the one remaining wildcard in a trial whose outcome is all but certain to end in acquittal.

Roberts, who didn’t respond to a question this week about possibly casting the deciding vote, is facing pressure from Democrats to allow witnesses, after they unsuccessfully attempted to insert a similar provision in the impeachment rules.

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But GOP senators say they do not believe Roberts will, or even should, cast the make-or-break vote on witnesses, arguing it would be a departure from how they view his role, as ceremonial arbitrator, and put the chief justice in the middle of a fierce political fight in an election year.

Sen. Josh Hawley Joshua (Josh) David HawleyRenewed focus on Trump's Supreme Court list after Ginsburg's death What Facebook's planned change to its terms of service means for the Section 230 debate Republican Senators raise concerns over Oracle-TikTok deal MORE (R-Mo.) acknowledged that he had not spoken to Roberts about the issue, but predicted the chief justice would not put himself at the center of the witness battle.

“I certainly think it’s a very fraught topic,” Hawley said. “I would guess that he would not break a tie.”

Senate Rules Committee Chairman Roy Blunt Roy Dean BluntMcConnell locks down key GOP votes in Supreme Court fight Murkowski: Supreme Court nominee should not be taken up before election Battle lines drawn on precedent in Supreme Court fight MORE (R-Mo.) said a 50-50 vote would mean the push for witnesses failed.

Asked if he thought Roberts would break the tie, Blunt responded: “He would not.”

Sen. Mike Braun Michael BraunPessimism grows as hopes fade for coronavirus deal McConnell shores up GOP support for coronavirus package Patient Protection Pledge offers price transparency MORE (R-Ind.) indicated Roberts shouldn’t break a tie, noting “he would be taking a side there” if he did.

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Meanwhile, Sen. John Cornyn John CornynCalls grow for Biden to expand election map in final sprint Bipartisan praise pours in after Ginsburg's death Chamber of Commerce endorses McSally for reelection MORE (R-Texas), an adviser to Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellOcasio-Cortez to voters: Tell McConnell 'he is playing with fire' with Ginsburg's seat McConnell locks down key GOP votes in Supreme Court fight Video shows NYC subway station renamed after Ruth Bader Ginsburg MORE (R-Ky.), argued there was no specific language that allowed Roberts to vote and break a tie.

“He doesn’t have any role other than to ceremonially preside,” Cornyn said.

Roberts inserted himself into the impeachment trial as senators were debating the trial rules last week. After a heated back-and-forth between House Judiciary Committee Chairman Jerrold Nadler Jerrold (Jerry) Lewis NadlerSchumer: 'Nothing is off the table' if GOP moves forward with Ginsburg replacement Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence House passes bill to protect pregnant workers MORE (D-N.Y.) and Jay Sekulow Jay Alan SekulowNow, we need the election monitors Judge denies Trump's request for a stay on subpoena for tax records Judge throws out Trump effort to block subpoena for tax returns MORE, Trump’s personal attorney, Roberts called out both sides for their rhetoric.

“It is appropriate at this point for me to admonish both the House managers and president’s counsel in equal terms to remember that they are addressing the world’s greatest deliberative body,” Roberts warned during a middle-of-the-night debate.

But since then Roberts has largely taken a passive role in the impeachment proceedings, only weighing in on Tuesday to indicate to Trump’s legal team and the House managers that he would like them to keep their responses to five minutes during the two-day question-and-answer session.

The swirl of speculation around Roberts comes as McConnell scrambles to lock down the 51 votes needed to block new trial witnesses.

Whether or not Roberts is willing to break a tie has consequences for the Republican whip effort. If Roberts were to signal he would break a tie and side with Democrats to allow witnesses, McConnell would need 51 senators to have an outright majority. That would allow him to lose no more than two Republican senators.

If Roberts did not break a tie, that would allow McConnell to still block witnesses if the vote was 50-50.

Several GOP senators — including Sens. Susan Collins Susan Margaret CollinsMcConnell locks down key GOP votes in Supreme Court fight Most Americans think winner of election should pick next Supreme Court justice: poll Murkowski: Supreme Court nominee should not be taken up before election MORE (Maine), Lisa Murkowski Lisa Ann MurkowskiMcConnell locks down key GOP votes in Supreme Court fight Most Americans think winner of election should pick next Supreme Court justice: poll Murkowski: Supreme Court nominee should not be taken up before election MORE (Alaska), Lamar Alexander Andrew (Lamar) Lamar AlexanderMcConnell locks down key GOP votes in Supreme Court fight Alexander backs vote on Trump Supreme Court nominee: What Democrats 'would do if the shoe were on the other foot' Toobin: McConnell engaging in 'greatest act of hypocrisy in American political history' with Ginsburg replacement vote MORE (Tenn.) and Mitt Romney Willard (Mitt) Mitt RomneyGOP set to release controversial Biden report McConnell locks down key GOP votes in Supreme Court fight Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? MORE (Utah) — have not yet revealed their position on an initial vote to allow witnesses.

Romney has said he wants to hear from former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE, while Collins has characterized herself as “very likely” to support calling witnesses. Both have stressed they will make a final decision after senators ask questions on Wednesday and Thursday.

“I have no idea how the votes are going to fall,” Collins told reporters on Wednesday.

If both Collins and Romney vote for witnesses, that would still leave McConnell with 51 GOP votes.

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In normal Senate procedure, a 50-50 tie could be broken by Vice President Pence. But Pence does not have a role in the impeachment trial, kicking the issue over to Roberts.

There were no ties in the 1999 Clinton trial, but Chief Justice Salmon Chase broke two ties during President Andrew Johnson’s impeachment trial in 1868.

Democrats tried but failed to get language in the rules resolution that would allow Roberts to rule on motions for new witnesses or documents.

An amendment offered by Sen. Chris Van Hollen Christopher (Chris) Van HollenDemocrats fear Russia interference could spoil bid to retake Senate Mid-Atlantic states sue EPA over Chesapeake Bay pollution Trump payroll-tax deferral for federal workers sparks backlash MORE (D-Md.) stated: “The Presiding Officer shall rule to authorize the subpoena of any witness or any document that a Senator or a party moves to subpoena if the Presiding Officer determines that the witness or document is likely to have probative evidence relevant to either article of impeachment before the Senate.”

A Senate Democratic aide noted at the time that the resolution was not intended to allow Roberts to break a tie, but instead make a ruling on requests for witnesses or documents. If the Senate disagreed, they could overrule him if they had 51 votes.

The Senate rejected Van Hollen’s amendment in a 53-47 party line vote.

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If Roberts injects himself into the middle of the witness fight, it would hardly be the first time he’s rankled Republicans.

Roberts last year sided with the court’s liberal wing to invalidate the Trump administration’s decision to add a citizenship question to the 2020 census. In 2012, he sparked fierce backlash from conservatives when he sided with Democratic-appointed justices to uphold ObamaCare’s individual mandate.

But Democrats are keeping up the pressure for Roberts to take the reins of what new witnesses or documents are allowed or not allowed.

Senate Minority Leader Charles Schumer Chuck SchumerRepublican senator says plans to confirm justice before election 'completely consistent with the precedent' Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Graham signals support for confirming a Supreme Court nominee this year MORE (D-N.Y.) knocked Republicans for trying to box out Roberts, saying they were “afraid of any independent analysis.”

“The Senate rules would allow the Senate to overrule Roberts, but the weight of his ruling would matter,” Schumer added when asked if Roberts should “step in.”

“And we liked that,” he said. “And we hoped that could happen.”