By Richard Cowan, Lisa Lambert and Patricia Zengerle
WASHINGTON (Reuters) - Another pivotal Republican announced opposition on Friday to calling witnesses in President Donald Trump's U.S. Senate impeachment trial, appearing to doom a bid by Democrats to permit testimony and paving the way for his expected acquittal.
Senator Lisa Murkowski said she carefully considered the need for witnesses and documents in the trial that will determine whether Trump is removed from office, but ultimately decided against it. A vote on allowing witnesses, such as former national security adviser John Bolton, is due later in the day.
Trump's fellow Republicans so far have blocked witnesses and new evidence, and have tried to expedite the process to secure a quick acquittal. Democrats, who called a trial without witnesses a sham, need four Republicans to join them to win a vote on the issue. Two of the 53 Republicans in the 100-seat Senate, moderates Mitt Romney and Susan Collins, have come out in favor.
Murkowski said in a statement that the charges of abuse of power and obstruction of Congress brought against Trump by the Democratic-led House of Representatives on Dec. 18 were rushed and flawed.
"Given the partisan nature of this impeachment from the very beginning and throughout, I have come to the conclusion that there will be no fair trial in the Senate. I don't believe the continuation of this process will change anything. It is sad for me to admit that, as an institution, the Congress has failed," Murkowski said.
The timing of a final vote on whether to convict or acquit was unclear. Republican senators had said it could come late on Friday or on Saturday. But some senators said on Friday the final vote may be held next week, as late as Wednesday.
Patty Murray, a member of the Senate Democratic leadership, told reporters that "all signs point to a rushed acquittal of an impeached president."
The Senate resumed the proceedings on Friday with the House Democrats who are serving as prosecutors making a final pitch for witnesses.
Adam Schiff, the lead Democratic prosecutor, said the Senate will be voting just hours after the New York Times reported new details from Bolton's unpublished book manuscript in which the former aide said Trump directed him in May to help in a pressure campaign to get Ukraine to pursue investigations that would benefit Trump politically.
Schiff noted that Trump denied Bolton's account.
"So here you have the president saying John Bolton is not telling the truth. Let's find out," Schiff told the Senate. "Let's put John Bolton under oath. Let's find out who's telling the truth. A trial is supposed to be a quest for the truth. Let's not fear what we will learn."
A two-thirds Senate majority is required to remove Trump. No Republicans have yet indicated they will vote to convict.
"If my Republican colleagues refuse to even consider witnesses and documents in this trial, this country is headed towards the greatest cover-up since Watergate," Chuck Schumer, the top Senate Democrat, told reporters, referring to the corruption scandal that prompted Richard Nixon in 1974 to become the only U.S. president to resign.
Republican Senator Lamar Alexander, who had been undecided, announced late on Thursday he would oppose witnesses. He said Democrats had proven the case against Trump but that the president's actions did "not meet the United States Constitution's high bar for an impeachable offense."
The House charged Trump with abuse of power for asking Ukraine to investigate political rival Joe Biden and with obstruction of Congress for blocking current and former officials from providing testimony or documents to the House.
Trump, only the third president in U.S. history to be impeached, denies wrongdoing and has accused Democrats of an "attempted coup."
Trump is seeking re-election in a Nov. 3 vote. Biden is a leading contender for the Democratic nomination to face him.
NEW BOLTON ACCUSATIONS
The New York Times, which previously reported on allegations made in Bolton's manuscript that go to the heart of impeachment charges, on Friday reported on additional material in the book.
The Times had reported that Bolton - contradicting Trump's version of events - wrote that the president told him he wanted to freeze $391 million in security aid to Ukraine until Kiev pursued investigations of Democrats, including Biden and the former vice president's son, Hunter Biden.
On Friday, the Times reported that Bolton also wrote that Trump directed him in May to assist in a pressure campaign to get damaging information on Democrats from Ukrainian officials.
Bolton wrote that Trump issued the order in a White House conversation that also included acting White House Chief of Staff Mick Mulvaney, personal lawyer Rudy Giuliani and White House Counsel Pat Cipollone, who is part of the president's impeachment defense team, the Times reported.
Bolton wrote that Trump told him to call Ukrainian President Volodymyr Zelenskiy to ensure Zelenskiy would meet with Giuliani, a key player in the campaign, the Times reported.
Robert Costello, a lawyer for Giuliani, called the Times report "categorically untrue."
Democrats have said Trump abused his power by using the security aid - passed by Congress to help Ukraine battle Russia-backed separatists - and a coveted White House invitation to Zelenskiy as leverage to get a foreign power to smear a political rival.
Like Alexander, who said it was "inappropriate for the president to ask a foreign leader to investigate his political opponent and to withhold United States aid to encourage that investigation," other Republicans who opposed witnesses also put out statements critical of Trump.
Republican Senator Rob Portman called Trump's asking Ukraine to investigate a political rival and delaying aid "wrong and inappropriate."
Republican Senator Marco Rubio said, "Just because actions meet a standard of impeachment does not mean it is in the best interest of the country to remove a president from office."