By Susan Cornwell and Patricia Zengerle

WASHINGTON (Reuters) – Saying “it is time for this to end,” President Donald Trump’s legal team appealed to the U.S. Senate on Tuesday to acquit him in his impeachment trial and sought to marginalize former national security adviser John Bolton’s explosive allegations about Trump’s conduct.

Trump’s lawyers wrapped up their third and final day of opening arguments, with the crucial question of calling trial witnesses including Bolton still unresolved in a Senate controlled by the president’s fellow Republicans and almost certain to vote to keep him in office as he seeks re-election on Nov. 3.

“The election is only months away. The American people are entitled to choose their president. Overturning past elections and massively interfering with the upcoming one would cause serious and lasting damage to the people of the United States and to our great country. The Senate cannot allow this to happen,” White House Counsel Pat Cipollone told the Senate.

“It is time for this to end, here and now. So we urge the Senate to reject these articles of impeachment.”

The next phase of the trial involves questions from the 100 senators to the lawyers representing Trump and the seven House of Representatives Democrats who have served as prosecutors. The Democratic-led House on Dec. 18 impeached the businessman-turned-politician on charges of abuse of power and obstruction of Congress arising from his request that Ukraine investigate political rival Joe Biden.

Adam Schiff, who served as the lead Democratic prosecutor in arguing the case against Trump last week, said the question remained as to whether the trial would be fair or unfair, with Republicans refusing so far to allow any witness testimony or new evidence.

“A fair trial involves witnesses and it involves documents,” Schiff told reporters.

The Senate may resolve the issue of whether to call witnesses in a vote on Friday or Saturday.

Trump’s legal team sought to minimize the importance of Bolton’s unpublished book manuscript that describes Trump’s central role in a pressure campaign aimed at getting Ukraine to investigate Biden, a leading contender for the Democratic nomination to face Trump in this year’s election.

“You cannot impeach a president on an unsourced allegation,” Trump’s personal lawyer Jay Sekulow told the Senate.

Directly contradicting Trump’s account of events, Bolton wrote in the manuscript that the president told him he wanted to freeze $391 million in security aid to Ukraine until Kiev pursued investigations into Democrats, including Biden and his son Hunter Biden, the New York Times reported.

Bolton’s allegations go to the heart of impeachment charges against Trump. Democrats have said Trump abused his power by using the security aid – approved by Congress to help Ukraine battle Russia-backed separatists – as leverage to get a foreign power to smear a political rival.

Sekulow underscored what fellow Trump legal team member Alan Dershowitz told senators late on Monday – that even if what Bolton says is true, it would not represent impeachable conduct.

Bolton left his White House post last September. Trump has said he fired Bolton. Bolton said he quit after policy disagreements.

Trump has denied telling Bolton he sought to use the Ukraine aid as leverage to get Kiev to investigate the Bidens. He has denied any quid pro quo – a Latin term meaning a favor for a favor – in his dealings with Ukraine.

‘I’D CALL IT INADMISSIBLE’

Sekulow told the senators they were taking part in “the most solemn of duties under our constitutional framework: the trial of the leader of the free world, the duly elected president of the United States. It is not a game of leaks and unsourced manuscripts. That’s politics, unfortunately.”

“Responding to an unpublished manuscript that may be – some reporters have an idea of maybe what it says – that’s what the evidence (is) – if you want to call that evidence. I don’t know what you’d call that. I’d call it inadmissible,” Sekulow added.

Trump’s fellow Republicans hold 53 seats in the Senate. A two-thirds majority is needed to remove him from office under the U.S. Constitution.

Some Republican senators who oppose calling witnesses proposed that Bolton’s manuscript be made available for senators to review on a classified basis, an idea rejected by top Senate Democrat Chuck Schumer.

“What an absurd proposal. It’s a book,” Schumer told reporters about the proposal floated by Republican Senators Lindsey Graham and James Lankford, saying there was no need to place the manuscript for review in a classified setting “unless you want to hide something.”

Lankford urged Bolton to speak publicly outside of the trial.

Schumer criticized Trump’s legal team for stating during its arguments to the Senate that there was no eyewitness testimony detailing abuse of power by Trump, “when we know that John Bolton has eyewitness testimony and is willing to testify.”

Schumer made a fresh appeal for four Republican senators – the number needed for a majority – to join Democrats in voting to call witnesses. Schumer also indicated Democrats would reject any effort at a so-called witness swap with Republicans.

“The Republicans can call who they want. They have the ability. They have the majority,” Schumer said.

Sekulow sought to portray Trump as the victim of scheming by Washington insiders dating back to his 2016 candidacy. Sekulow listed grievances that Trump raised about prior investigations including the special counsel probe that documented Russian interference in the 2016 election to boost his candidacy and his campaign’s numerous contacts with Moscow.

The impeachment drive against Trump, Sekulow argued, was a partisan exercise motivated by Democratic opposition to Trump’s policies, not genuine impeachable offenses.

“But to have a removal of a duly elected president based on a policy disagreement?” Sekulow asked. “That is not what the framers (of the Constitution) intended. And if you lower the bar that way – danger, danger, danger. Because the next president or the one after that, he or she would be held to that same standard? I hope not. I pray not.”

(Reporting by Susan Heavey, Susan Cornwell, Makini Brice, Karen Freifeld, David Morgan, Patricia Zengerle and Richard Cowan; Writing by Will Dunham; Editing by Jonathan Oatis, Bernadette Baum and Peter Cooney)