"This is preposterous that this would not be an impeachable offense, that this standard in America is now that presidents could abuse their power to help in elections", Booker said.
The historic third presidential impeachment trial resumes on Tuesday, placing senators in the unusual position of serving as both judge and jury as they close in on rendering a verdict in the case of President Donald Trump.
House Democrats charge that Trump abused his office by withholding $400 million in security aid and a White House meeting from Ukraine while pressuring Kiev to open investigations into the President's political rivals.
Tuesday begins with opening arguments by the House managers, as they're called, a discussion that could span several days, depending on a debate over rules that could take up some time.
Democrats are demanding that the Senate agree to subpoena crucial documents and four current and former senior White House officials to testify.
The Trump team refutes the allegation that he pressed Ukrainian President Volodymyr Zelenskyy to launch an investigation into Joe Biden.
The House's impeachment managers are working through the weekend and will be at the Capitol midday Sunday to prep the case.
In the 46-page trial memorandum, the House impeachment managers asserted that beginning in the spring, Mr Trump undertook a corrupt campaign to push Ukraine to publicly announce investigations of his political rivals, withholding as leverage almost US$400 million in military aid and a White House meeting.
Dershowitz was repeating a line of argument that we've heard before from Trump's staunchest defenders.
The White House signaled this week what it expects will happen: no witnesses. Murkowski said she would vote with other Republicans to hold off on that decision until the second phase of the impeachment proceedings.
"There's no need for witnesses", he said.
"The president should be acquitted".
The heavily footnoted document, formatted in the style of a courtroom filing, was headlined "In re Impeachment of President Donald J. Trump" and addressed to the Senate, "sitting as a court of impeachment".
There's likely to be a motion to dismiss the charges outright, though that is doomed to fail, as well as a motion to include witnesses, a move that may not initially earn any GOP support.
Senate Minority Leader Chuck Schumer, D-N.Y., talks to reporters about the impeachment trial of President Donald Trump on charges of abuse of power and obstruction of Congress, at the Capitol in Washington, Thursday, Jan. 16, 2020. But because there are only 47 Democrats (and 53 Republicans), the president is widely expected to be cleared.
He added: "I still think we should wait and see what comes out in the trial itself".
"I tend to believe having additional information would be helpful". The managers will do a walk-through of the Senate chamber on Monday. So far, no Republicans have indicated a willingness to do so. The proposition was "amply rebutted" by the House managers in the Johnson case, Bowman said.
Hunter worked for a Ukrainian company when Joe Biden was U.S. vice-president.
The brief calls on senators to conduct a fair trial as part of the oath they took last week to "do impartial justice".
That would provoke a showdown.
"Rubbish", said Frank Bowman, a University of Missouri law professor and author of his own book about the history of impeachment for the Trump era.
He meanwhile warned Republicans who don't support the White House witness demands. "I don't know what Hunter Biden has to do with the phone call that was made..." "Seriously. That's what it is", he said.