President Donald Trump's defense team repeatedly argued on Saturday that there isn't enough evidence to impeach him because Congress hasn't heard from any witnesses who had "direct contact" with the president.

Democratic lawmakers seized on those statements, saying they underscore the need to call more firsthand witnesses in Trump's trial.

Moreover, while Trump's lawyers complain of not hearing testimony from direct witnesses, the defense could easily solve that problem by retracting Trump's sweeping directive barring all executive branch officials across six agencies from cooperating with Congress' impeachment inquiry.

"The president's counsel did something that they did not intend: they made a really compelling case for why the Senate should call witnesses and documents," Senate minority leader Chuck Schumer said after opening arguments on Saturday.

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President Donald Trump's defense team consistently drilled down on one key point as it began opening arguments in his impeachment trial on Saturday: the evidence against Trump is limited, at best, and he can't be impeached because the public hasn't heard direct evidence of his misconduct from him or anyone close to him.

The remarks came as Republicans and Democrats in the Senate fight over whether to call new witnesses in the president's trial.

Democrats argue that while they have more than enough to impeach Trump, they still haven't heard from senior executive branch officials closest to the president who could shed more light on his efforts to pressure Ukraine into interfering in the 2020 election.

Republicans, meanwhile, say that if the evidence against Trump is as overwhelming as House Democrats say it is, the Senate doesn't need to call new witnesses.

But on Saturday, Trump's lawyers seemed to bolster Democrats' case by repeatedly claiming that they hadn't heard from a single witness who had "direct contact" with the president.

Although their statements were misleading (Gordon Sondland, the US's ambassador to the European Union, was in frequent touch with Trump and testified to Congress that the president engaged in a quid pro quo with Ukraine), Democratic lawmakers noted that the comments underscored the need to hear from more firsthand witnesses.

It's worth noting, too, that though the president's lawyers complain of not hearing testimony from witnesses who spoke to Trump directly, the defense team led by White House counsel Pat Cipollone could easily solve that problem by retracting Trump's sweeping directive last year barring all executive branch officials across six agencies from cooperating with the House of Representatives' impeachment inquiry.

Multiple senior administration officials in the president's inner circle — like acting White House chief of staff Mick Mulvaney, Secretary of State Mike Pompeo, and former national security adviser John Bolton — cited Cipollone's command, which he issued at the president's direction, as the reason they would not testify or provide relevant documents.

Bolton, who was at the center of a number of episodes investigated in the inquiry, has since said that he will testify if the Senate decides to subpoena him.

"Now, the first point that I would like to make is that the president's counsel did something that they did not intend: They made a really compelling case for why the Senate should call witnesses and documents," said Senate minority leader Chuck Schumer.

"They kept saying there are no eyewitness accounts, but there are people who have eyewitness accounts, the very four witnesses and the very four sets of documents that we have asked for," he said. "But there are people who do know. Mick Mulvaney knows. In all likelihood, Mr. [Robert] Blair, [an aide to Mulvaney], knows. Mr. Bolton may know. 'Why shouldn't we have witnesses and documents here?' I thought."

Sen. Joe Manchin of West Virginia, who is widely considered a Democratic swing vote because he represents a deep-red state, told CNN he thought Trump's team did a "good job" of "making me think about things." He added, "One thing that stuck in my mind is they said there isn't a witness they have had so far that had direct contact with the president. I'd love to hear from Mulvaney and Bolton."

Sen. Chris Murphy of Connecticut echoed that point, telling MSNBC that Trump's lawyers "repeatedly said that we have heard limited evidence from individuals who talked directly to the president, who were ordered by the president to engage in this scheme."

"Of course, the reason for that is because the White House won't let us hear" from those people, he added. "So if what's missing ... is direct evidence of what the president told the people who work for him, there's a way to solve for that. I hope we don't have to get leaked audio of the president directing orders in this corruption scheme in order to prove our case."

He was referring to a bombshell report from ABC News this week which said the outlet had obtained an audio tape from 2018 where Trump is heard ordering the firing of Marie Yovanovitch, who at the time the US's ambassador to Ukraine.

The president demanded she be removed after his personal lawyer, Rudy Giuliani, colluded with a controversial op-ed columnist and two Ukrainian associates, Lev Parnas and Igor Fruman, to plant negative stories about Yovanovitch in the press accusing her of anti-Trump bias.

"Get rid of her!" Trump is heard saying in the recording. "Get her out tomorrow. I don't care. Get her out tomorrow. Take her out. OK? Do it."

Parnas' attorney, Joseph Bondy, said Fruman created the original recording and gave Parnas a copy. Bondy turned the copy over to the House Intelligence Committee.

Editor's note: A previous version of this article incorrectly stated Lev Parnas recorded President Trump ordering the firing of Marie Yovanovitch. In fact, Igor Fruman created the recording and gave Parnas a copy. The article has been updated to reflect this correction.