By Susan Cornwell and Patricia Zengerle

“You cannot impeach a president on an unsourced allegation,” Trump personal lawyer Jay Sekulow told the Senate, referring to Bolton’s unpublished book manuscript that describes Trump’s central role in a pressure campaign aimed at getting Ukraine to investigate political rival Joe Biden.

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.

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.

Trump is seeking re-election on Nov. 3. Biden is a leading candidate for the Democratic nomination to oppose Trump.

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 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“Responding to an unpublished manuscript that may be – some reporters have an idea of maybe what it says – that’s what the evidence (is) – if you want to call that evidence.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.

Some Republican senators 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.

Schumer stepped up his party’s calls for Bolton to be summoned as a trial witness. Senate Republicans, who have so far refused to allow any witnesses or new evidence in the trial, faced mounting pressure from Democrats and some moderates in their own party to summon Bolton.

The trial will determine whether Trump is removed from office after being impeached by the Democratic-led House of Representatives last month on charges of abuse of power and obstruction of Congress arising from his conduct toward Ukraine.

Trump is expected to be acquitted in the 100-seat Senate, where Republicans hold 53 seats and a two-thirds majority is needed to remove him from office under the U.S. Constitution.

‘MAKES SENSE’

“Looking at the manuscript makes sense to me. But we’re not going to just call John Bolton. If you call John Bolton, we’re calling everybody. We’re not just going to call one witness,” said Republican Senator Lindsey Graham, a close Trump ally who was at the White House on Tuesday morning.

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

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.

Lankford late on Monday urged Bolton to speak publicly outside of the impeachment trial.

“John Bolton is no shrinking violet,” Lankford said in a video posted to his Facebook page. “My encouragement would be: If John Bolton’s got something to say, there’s plenty of microphones all over the country – that he should step forward and start talking about it right now.”

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.

‘DANGER, DANGER, DANGER’

The impeachment drive against Trump, Sekulow argued, was a partisan exercise motivated by policy differences that Democrats have with Trump, not genuine impeachable offenses.

“But to have a removal of a duly elected president based on a policy disagreement? 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.”

The Senate may resolve the issue of whether to call witnesses in a vote on Friday or Saturday. Some moderate Republican senators, including Mitt Romney and Susan Collins, said the disclosures were likely to sway at least four Republicans to call Bolton to testify, which would give Democrats the votes necessary in the Republican-led Senate to summon him.

The focus was on whether two other moderate Republicans, Lamar Alexander and Lisa Murkowski, would vote to hear from Bolton.

Romney told Reuters on Tuesday that the idea of a “one-for-one” witness deal, with one witness called by Democrats and one by Republicans, “has merit,” but added: “I wouldn’t suggest any particular names.”

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