A key group of Republican senators stole the spotlight on Thursday, using a marathon session of the Senate impeachment trial to challenge both 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 legal team and House managers.

Senators asked more than 80 questions during the nine-hours-long session with controversial figures ranging from the whistleblower whose report helped spark the impeachment inquiry to Trump’s personal attorney Rudy Giuliani Rudy GiulianiDemocrats fear Russia interference could spoil bid to retake Senate Grand jury adds additional counts against Giuliani associates Lev Parnas and and Igor Fruman Juan Williams: Breaking down the debates MORE to 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 getting name checks.

While many senators offered easy, leading questions to those defending their party’s interests, the most intriguing moments came from a core group of undecided senators in both parties, sparking a round of attempted tea leaves readings ahead of Friday’s crucial vote on whether to call additional witnesses.

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Sen. 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 (R-Alaska) immediately captured headlines when she asked the White House defense team why the Senate should not call Bolton to testify after The New York Times reported that he will claim, in his forthcoming memoir, that Trump tied Ukraine aid to the country helping investigate Democrats, including former Vice President Joe Biden Joe BidenBiden leads Trump by 36 points nationally among Latinos: poll GOP set to release controversial Biden report Can Donald Trump maintain new momentum until this November? MORE and his son Hunter Biden.

“This dispute about material facts weighs in favor of calling additional witnesses with direct knowledge. Why should this body not call Ambassador Bolton,” Murkowski asked in a question posed to the White House defense team.

Murkowsi and Sens. Kyrsten Sinema (D-Ariz.), Joe Manchin Joseph (Joe) ManchinNames to watch as Trump picks Ginsburg replacement on Supreme Court Momentum growing among Republicans for Supreme Court vote before Election Day Gardner on court vacancy: Country needs to mourn Ginsburg 'before the politics begin' MORE (D-W.Va.) and 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 (R-Maine) also took veiled shots at Giuliani. Collins and Murkowski are undecided on impeachment witnesses, while Sinema and Manchin are viewed as potential Democratic votes to acquit Trump.

“Will the president assure the American public that private citizens will not be directed to conduct American foreign policy or national security policy unless they have been specifically and formally designated by the president and the State Department to do so?” they asked.

Giuliani, Democrats say, led the effort to oust former U.S. Ambassador to Ukraine Marie Yovanovitch Marie YovanovitchGrand jury adds additional counts against Giuliani associates Lev Parnas and and Igor Fruman Strzok: Trump behaving like an authoritarian Powell backs Biden at convention as Democrats rip Trump on security MORE and then push Ukrainian representatives to open two investigations that would benefit Trump politically.

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Collins was also part of a group of Republican senators who questioned if it was ever appropriate for a president to ask for a foreign country to investigate a U.S. citizen, including a political rival. Trump, in a July 25 phone call, asked Ukrainian President Volodymr Zelensky to help “look into” the Bidens.

Murkowski and Collins were spotted having a lengthy, animated conversation with a top McConnell staffer late Thursday night. Sen. Cory Gardner Cory Scott GardnerMcConnell locks down key GOP votes in Supreme Court fight Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 MORE (R-Colo.), an endangered GOP incumbent who has announced he will vote against allowing witnesses, hovered nearby.

Sen. 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 (R-Tenn.), who is expected to announce a decision on witnesses imminently, caught the attention of reporters he chatted with McConnell’s top floor staffer and delivered a note to the GOP leader in the middle of Thursday’s session.

Murkowski and Alexander also joined with Sens. Ted Cuz (R-Texas), Pat Toomey Patrick (Pat) Joseph ToomeyAppeals court rules NSA's bulk phone data collection illegal Dunford withdraws from consideration to chair coronavirus oversight panel GOP senators push for quick, partial reopening of economy MORE (R-Pa.), Dan Sullivan Daniel Scott SullivanWill Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Republican Senators raise concerns over Oracle-TikTok deal MORE (R-Alaska) and Lindsey Graham Lindsey Olin GrahamMcConnell locks down key GOP votes in Supreme Court fight Will Republicans' rank hypocrisy hinder their rush to replace Ginsburg? Momentum growing among Republicans for Supreme Court vote before Election Day MORE (R-S.C.), all four of whom are expected to vote against witnesses, to ask that even if Bolton did testify “isn’t it true that the allegations still would not rise to the level of an impeachable offense and that therefore for this and other reasons his testimony would add nothing to this case.”

The question caught the attention of reporters because it mirrors the argument echoed by several Republicans in recent days: that even if Bolton is telling the truth that it still wouldn’t warrant removing Trump from office and so it wouldn't change the outcome of the trial.

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Alexander was spotted chatting and joking with Sens. Maria Cantwell Maria Elaine CantwellHillicon Valley: Zuckerberg acknowledges failure to take down Kenosha military group despite warnings | Election officials push back against concerns over mail-in voting, drop boxes Bipartisan senators call for investigation of popular fertility app The Hill's Coronavirus Report: Mike Roman says 3M on track to deliver 2 billion respirators globally and 1 billion in US by end of year; US, Pfizer agree to 100M doses of COVID-19 vaccine that will be free to Americans MORE (D-Wash.) and Mark Warner Mark Robert WarnerIntelligence chief says Congress will get some in-person election security briefings Overnight Defense: Trump hosts Israel, UAE, Bahrain for historic signing l Air Force reveals it secretly built and flew new fighter jet l Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' House approves bill to secure internet-connected federal devices against cyber threats MORE (D-Va.) during the Senate’s last break of the day. Pat Philbin, a member of Trump’s legal team, briefly wandered over to say hello, prompting 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) to make an apparent joke about Alexander’s well known “Lamar!” campaign slogan.

“It’s like Bono. It’s like Cher,” Cornyn could be overheard saying on the floor. “Lamar!”

Alexander also spent several minutes thumbing through a copy of “Impeachment: An American History” by John Meacham. McConnell also read the book to help him prepare for the impeachment trial.

There were also tense moments during the question-and-answer session, like when Sen. Rand Paul Randal (Rand) Howard PaulSecond GOP senator to quarantine after exposure to coronavirus GOP senator to quarantine after coronavirus exposure The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE (R-Ky.) tried to get Chief Justice John Roberts to read a question related to the whistleblower at the center of the House impeachment inquiry.

"The presiding officer declines to read the question as submitted,” Roberts said after being handed the slip of paper by a Senate page.

The two men had been engaged in behind-the-scenes haggling over the contents of the question, which names the individual alleged to be the whistleblower.

Roberts indicated privately on Wednesday that he would not read the question, which would put him in the position of publicly outing the whistleblower on the Senate floor. Paul’s Republican colleagues had also publicly signaled they wanted him to back down, but to no avail.

"We’ve been respectful of the chief justice’s unique position in reading our questions,” 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.) said at the start of Thursday’s session. “And I want to assure him that that level of consideration for him will continue.”

The question-and-answer session comes as the Senate is prepared to vote Friday on whether or not to call new witnesses.

As of Thursday night several Republican senators have not said how they will vote on an up-and-down question about allowing new witnesses and documents to be requested as part of the Senate trial.

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McConnell can lose three GOP votes and still block new witnesses, as long as Roberts doesn’t step in to break a tie. He could lose two GOP senators and win the vote outright.

House Intelligence Committee Chairman Adam Schiff Adam Bennett SchiffTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Overnight Defense: House to vote on military justice bill spurred by Vanessa Guillén death | Biden courts veterans after Trump's military controversies MORE (D-Calif.) made a pitch to GOP senators that if they allowed witnesses Democrats would agree to limit closed-door depositions to one week. The offer appeared aimed at undercutting the Republican argument that calling in witnesses would eat up weeks, if not months, of time.

“Are we really driven by the timing of the State of the Union? Should that be our guiding principle? Can we take one week to hear from these witnesses? I think we can. I think we should. I think we must,” he said.

Schiff added that if there is any dispute over whether a witness is “relevant or probative” to the issues, or if there are objections over claims of executive privilege, Roberts would be able to make the ultimate call on the matter.

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, a lawyer on the White House defense team, dismissed the idea out of hand, saying that under such a format, they would not be able to call any of the witnesses they want, like the Bidens or the anonymous whistleblower who first brought forward the allegations about Ukraine.

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“I think the irony of this,” Sekulow said, is “that we can call anyone we want except the witnesses we want.”

Still, Republicans are projecting cautious optimism that they’ll be able to defeat the witness vote and move quickly to decide whether to convict and remove Trump from office.

Trump is expected to be acquitted in the GOP-controlled chamber, with Democrats needing 20 Republican senators to flip to their side to successfully push Trump out of the Oval Office.

Sen. John Barrasso John Anthony BarrassoMurkowski: Supreme Court nominee should not be taken up before election Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE (Wyo.), the No. 3 Republican senator, said that the caucus was prepared to go late Friday if Democrats try to use procedural delaying tactics to drive a final vote late into the night.

“Sen. Schumer would be able to amend that. The question is does he try 11 [times],” Barrasso said. “Once he realizes how it’s going to turn out.”