Updated at 1:57 p.m. ET
Senators weighing impeachment charges against President Trump are spending Thursday firing questions at lawyers as they did the day before, just as the prospect of John Bolton's appearance as a witness continues to stoke speculation.
Watch the proceedings live beginning at 1 p.m. ET.
Roberts refuses early question
U.S. Chief Justice John Roberts, presiding over the trial, refused to read a question from Sen. Rand Paul, R-Ky.
It was believed that Paul's question would have identified the whistleblower whose complaint sparked the House's impeachment investigation of Trump.
The person's identity is protected by law and neither Roberts nor Majority Leader Mitch McConnell, R-Ky., want it to be in the official trial record. McConnell had urged senators to be respectful of Roberts, who is supervising the trial as specified in the Constitution while also attempting to keep above the partisan aspects.
"The presiding officer declines to read the question as submitted," Roberts said.
Acquittal at hand?
Republicans would like Trump to be acquitted as early as Friday, but Democrats are working behind the scenes to recruit enough members to support bringing in witnesses to testify.
That effort is flagging, senators say.
"The momentum is clearly in the direction of moving to final judgment on Friday," said Sen. John Barrasso, R-Wyo. "We still have a couple members who said they want to listen to answers to questions, but that's where the momentum is in the caucus right now."
Sen. Chuck Schumer, D-N.Y., also gave his assessment on where the votes stand on possibly bringing in witnesses. He tried to walk the tightrope.
"Probably no," Schumer told reporters. "But is it a decent, good chance? Yes."
Democrats need to persuade at least four Republicans to cross party lines in order to lock in enough votes to subpoena witnesses.
Speaking before Thursday's session, House manager Adam Schiff, D-Calif, charged the Trump administration has "gone to extraordinary lengths to put a muzzle on John Bolton to avoid calling him as a witness, to avoid letting the American people hear what he has to say."
Another House manager, Rep. Jerry Nadler D-N.Y. left the door open to the possibility that the House may subpoena Bolton if the Senate doesn't.
"We will see," Nadler said.
Republicans' witnesses
Meanwhile, Republicans spent some time on Wednesday saying that if the door is opened to witnesses, Republicans would like to call people such as former Vice President Joe Biden's son Hunter, who had served on a Ukrainian energy company board.
Republicans might also call the whistleblower.
Asked what kind of delay witnesses would add to the trial, Trump defense lawyer Jay Sekulow said "months."
Sekulow added: "This would be the first of many weeks."
Schiff, bristled at this argument, saying Trump's defense team is exaggerating the delay to discourage senators from supporting calling witnesses, including Bolton, the former national security adviser, whose possible appearance in the trial has captured Washington since revelations from his forthcoming book were publicly leaked.
"You can subpoena John Bolton," Schiff said. "Don't be thrown off by this claim, 'Oh, if you even think about it, we are going to make you pay with delays like you've never seen. We're going to call witnesses that will turn this into a circus.' It shouldn't be a circus. It should be a fair trial. You can't have a fair trial without witnesses."
Some Republicans have been discussing a possible deal involving a witness-for-witness swap, in which Bolton might be exchange for Hunter Biden. Sen. Lindsey Graham, R-S.C., said that if Republicans are able to call just one witness, it will be Hunter Biden.
"Because he's incredibly relevant to whether or not President Trump had a reason to believe that corruption was afoot in the Ukraine," Graham told reporters on Wednesday.
The end of the affair
Over eight hours of debate Wednesday, Democratic House managers and Trump's defense are making their final pitches ahead of a key vote on Friday on whether the Senate will hear from witnesses.
White House lawyer Patrick Philbin also defended accepting "credible" informationfrom foreign sources about someone running for public office, arguing that "mere information is not something that would violate the campaign finance laws."
Democrats, including Schiff and several senators, quickly lashed out. Schiff called that policy "corruption."
Also among the more striking responses: a question posed by Sen. Ted Cruz, R-Texas. Cruz asked whether a president ordering a quid pro quo in the foreign policy arena was ever appropriate.
The question was relevant to the heart of the articles of impeachment, which center on an allegation that Trump conditioned hundreds of millions of dollars in military aid to Ukraine on the country announcing investigations into Trump's political rivals.
Alan Dershowitz, one of Trump's lawyers, took the sweeping view that if a quid pro quo is in the president's "electoral interest," then it should never result in an impeachment, a broad interpretation of the powers of the executive branch.
"If a president does something which he believes will help him get elected in the public interest, that cannot be the kind of quid pro quo that results in impeachment," Dershowitz said.
Dershowitz said if a president does not act out of purely a "corrupt motive," but rather has a "mixed motive," meaning a president is acting of the country's interest and in hopes of improving reelection prospects, then the behavior cannot warrant articles of impeachment.
"How many presidents have made foreign policy decisions after checking with their political advisers and pollsters?" he asked.
Sen. Richard Blumenthal, D-Conn., said that argument brought Dershowitz "into the land of legal absurdity." Furthermore, he tweeted, "That anything a public official does for re-election is OK. That cannot be true."
Evaluating the first of two days of question and answers, Sen. Bob Casey, D-Pa., said he did not think the day's proceedings changed any minds.
"I don't think so in large measure, but it does force everyone to confront issues that sometimes you haven't thought as much about or sometimes you are familiar with, but not to the level of depth that you should," Casey said.
With a strong Republican majority in the Senate, Trump is expected to be acquitted.
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