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Senators spent Thursday asking questions in President Trump’s impeachment trial, and that was apparently enough for two key Republican senators to come down on how they’ll vote Friday on whether to extend the trial by calling witnesses including former national security adviser John Bolton.

Below are the takeaways from the day.

1. Democrats almost certainly aren’t getting the four Republicans they need to call witnesses

The biggest news of the day came at the end of the trial’s question-and-answer session, at nearly 11 p.m. There are only four potential swing votes, and one of them, Sen. Lamar Alexander (R-Tenn.), said he won’t vote to call witnesses.

Alexander’s justification: He thinks Trump did what he’s accused of doing, but that doesn’t warrant removal from office.

Another swing vote, Sen. Susan Collins (R-Maine), said Thursday she would vote for witnesses. Mitt Romney (R-Utah) said he would “like to hear from Bolton.” That leaves Sen. Lisa Murkowski (R-Alaska), who says she’s “going to reflect … and read my notes” and will announce her decision Friday morning.

At this point, it’s possible the Senate is faced with a 50-50 split on whether to call witnesses, one vote shy of a decision. This is uncharted territory for the Senate, and for the Constitution.

It also likely means that after nearly two weeks of arguments and plenty of news outside the courtroom bolstering their case — like that Bolton has written in a book draft that Trump did directly tie Ukraine’s aid to the announcement of investigations — Democrats didn’t sway enough senators to call witnesses.

2. All eyes are on John Roberts

So what if there is a tie in Friday’s vote for witnesses? Could the chief justice break it by casting the deciding vote? That debate has been bubbling over the course of the Senate trial among academics and pundits. Now it will boil.

For example, law scholar Frank Bowman argued in SCOTUSblog earlier this month that Roberts can cast the tie-breaking vote in this case. He’s the presiding officer of the Senate, and when the vice president performs that function in regular Senate business, they cast a vote.

But there’s not consensus on that. Some legal scholars agree with Senate Republicans that a 50-50 vote simply means the motion failed. It’s not even clear who will get to decide whether Roberts gets to decide: Senate Majority Leader Mitch McConnell (R-Ky.), Roberts in his role as presiding official, or the Senate parliamentarian? Could the Senate vote on whether to allow Roberts to cast a tie vote?

So far Roberts has been deferential to the Senate and reluctant to drag himself — and his court — into such a partisan fight.

3. Trump’s defense still hasn’t answered key questions about his intent

When did Trump first pause the military aid to Ukraine? And when did he start talking to Ukraine about investigations into the Biden family?

Those are two key questions Republican senators asked of Trump’s defense on Wednesday, and Trump’s lawyers had no answer. White House Deputy Counsel Patrick Philbin acknowledged that there is no evidence of Trump having talked with Ukrainian officials about the Bidens before Joe Biden entered the 2020 race.

Understanding when Trump paused the aid and when he first became concerned about the actions of Biden and the former vice president’s son Hunter in Ukraine would go a long way in proving or disproving Democrats’ case that the president abused his power.

After having a day to think about how to address these questions to key votes on witnesses, they didn’t have any new answers.

4. Rand Paul’s attempt to publicly out the whistleblower

This week, Trump’s legal team evolved their defense of the president in the direction of: “So what if he did do it?” As they did, some Trump allies escalated their efforts to undermine House Democrats’ case in ways other than directly disputing the evidence.

On Wednesday, Sen. Rand Paul (R-Ky.) sent a question to the desk of the chief justice, who did not read it out loud. On Thursday, Paul tried again, and again Roberts refused. In the question, Paul mentioned a name that some media outlets have reported is the alleged whistleblower. We know what was in it, because Paul left the trial after his question was batted down and read it in full to a room of reporters.

Eventually, another Republican senator’s question of whether Schiff’s staff engaged with the whistleblower before he filed his complaint was read aloud. Schiff angrily called it a “smear.” (Schiff’s committee did get a heads-up about the existence of a whistleblower complaint before it got filed, but there is no evidence Schiff was working in concert with the whistleblower. Schiff has repeatedly said he has not met the whistleblower.)

“Members of this body used to care about the protection of whistleblower identities,” Schiff said. “They didn’t used to gratuitously attack members of committee staff, but now they do. … I think it’s disgraceful. Whistleblowers are a unique and vital resource for the intelligence community.”