Democratic House managers and President Donald Trump’s lawyers responded to senators’ questions for a second straight day on Thursday, hoping to reinforce their arguments for and against impeachment trial witnesses ahead of a crucial vote.

The opposing sides debated whether a president can legitimately request investigations into a political rival and whether a quid pro quo amounts to an impeachable offense.

In one tense moment Chief Justice John Roberts rejected a question from Sen. Rand Paul, R-Ky.

With the trial set to enter a new phase Friday, Republican lawmakers appeared more confident they will have enough votes to block motions for new witnesses and documents. At the same time, some moderate Republicans signaled they were likely to vote to call witnesses.

Here are five moments from the second day of questioning:

Can a president ever ask for investigations into a political rival?

Sen. Susan Collins, R.-Maine, asked House managers and Trump’s attorneys if there are legitimate circumstances under which a president can request for a foreign country to investigate a U.S. citizen, including a political rival.

“It would be hard for me to contemplate circumstances where that would be appropriate,” said lead House manager Rep. Adam Schiff, D-Calif.. Schiff also criticized the defense team’s claim that Trump had “mixed motives” for wanting investigations into the Bidens.

Alternately, Trump’s deputy White House counsel Patrick Philbin responded that it would “perfectly legitimate” for a president to make such a request.

“President Trump didn’t ask [Ukrainian President Volodymyr] Zelensky specially for an investigation,” Philbin said. Philbin asserted that President Trump was interested in the removal of a former Ukrainian prosecutor and the energy company Burisma, for which Hunter Biden was a board member.

Sen. Murkowski says Bolton book revelation ‘weighs in favor’ of calling witnesses

In a written question to Trump’s lawyers, Rep. Lisa Murkowski, a moderate Republican from Alaska, gave an indication of which way she is leaning on the question of whether to call witnesses.

Murkowski asked Trump’s lawyers why senators should not call former national security adviser John Bolton to testify in the trial. In her question, Murkowski referred to a New York Times report citing details from an upcoming book in which Bolton reportedly writes Trump told him aid should be withheld from Ukraine until the country agreed to announce investigations into the president’s political rivals.

“This dispute over material facts weighs in favor of calling additional witnesses with direct knowledge,” Murkowski wrote in her question.

In response to the question, Philbin said House Democrats chose not to subpoena Bolton during their impeachment inquiry. He added that the statements from Bolton’s manuscript have not been verified.

After the Senate adjourned, Murkowski said she needed the night to think over the question of witnesses. Two other GOP lawmakers — Sens. Susan Collins of Maine and Mitt Romney of Utah — said they will vote for witnesses. But Sen. Lamar Alexander, R-Tenn., told reporters he plans to vote against hearing from witnesses, likely tipping the vote in the White House’s favor and ensuring a quick end to the trial.

Is Roberts’ legitimacy in jeopardy?

2020 Democratic presidential candidate Sen. Elizabeth Warren, D-Mass., asked the House managers whether Roberts and the U.S. Supreme Court could lose legitimacy because Roberts is presiding over a trial in which Republican senators have refused to allow witnesses or evidence.

“This trial is part of our constitutional heritage, that we were given the power to impeach the president,” Schiff responded. “I don’t think a trial without witnesses reflects adversely on the chief justice. I do think it reflects adversely on us. I think it diminishes the power of this example to the rest of the world.”

Schiff argued that the Senate’s inability to hold a fair trial “will feed cynicism” among the American public.

Dershowitz’s quid pro quo argument is ‘normalization of lawlessness,’ Schiff says

Sen. Jon Tester, D-Mont., asked about Trump lawyer Alan Dershowitz’s assertion that if the president does something that will help him get elected but also believes his election is in the public interest, it cannot be an impeachable offense.

Schiff delivered a strong rebuke of Trump lawyer Dershowitz’s argument. He called Dershowitz’s argument “astonishing,” and said it showcased a “normalization of lawlessness” that has taken hold during the trial. “What we have seen over the last couple days is a decent into constitutional madness,” Schiff said. “That is an argument made of desperation.”

Roberts rejects Sen. Rand Paul’s question

Roberts asserted his power as the trial’s presiding officer by rejecting a question asked by Paul.

“The presiding officer declines to read the question as submitted,” Roberts said after receiving the written question and sitting with it in silence for several moments.

Roberts did not explain why he declined to read the question, but it later became clear that the question included the name of someone who conservatives have accused of being the whistleblower whose complaint sparked the impeachment inquiry.

Despite a rule that requires senators to remain in the chamber during the trial, Paul left the Senate to read his question aloud to reporters. Paul said he was “disappointed” by Roberts refusal to read the question.

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