President Donald Trump's lawyers on Tuesday completed their oral arguments in the Senate impeachment trial, bringing to a quick end a defense that attempted to discredit the evidence gathered by House Democrats in their initial probe.

The team used far fewer than its allotted 24 hours to make its case.

Deputy White House Counsel Pat Philbin began the day attempting to refute the House Democrats' "abuse of power" charge by questioning whether the House could judge the president's motives.

"How do we tell under the House managers' standard what an illicit motive is, when there's an illicit motive?" Philbin asked. "How are we supposed to get proof of what's inside the president's head?"

Philbin also argued that House Democrats' reliance on the testimony of White House officials to frame their case was flawed. Those officials testified during the House probe that a July 25 call between Trump and Ukraine President Volodymyr Zelenskiy — in which Trump pressed his counterpart to announce an investigation into his Democratic rivals while withholding congressionally approved military aid — was inappropriate.

Philbin said the president is ultimately not beholden to his subordinates' suggestions or opinions.

Trump "has the authority to set policies and make determinations regardless of what the staffers recommend," Philbin said.

The House voted last month to impeach Trump on articles of abuse of power and obstruction of Congress in relation to his dealings with Ukraine.

Trump's lawyer Jay Sekulow on Tuesday warned the Senate that "to lower the bar of impeachment" would weaken constitutional standards. He also said House Speaker Nancy Pelosi's decision to withhold the articles for a month after Trump's impeachment contradicted the sense of urgency around the issue Democrats hoped to establish.

Getting the impeachment done in the House before Christmas "was so critical," he said, but "they never really answered the question on why they thought there was such a national emergency."

The oral arguments come two days after a bombshell report that Trump told former National Security Advisor John Bolton that he wanted to withhold military aid to Ukraine in exchange for investigations into political rivals, including former Vice President Joe Biden and his son Hunter.

In Monday's arguments, Trump's lawyers ignored the news, based on an unpublished manuscript of Bolton's forthcoming memoir. But on Tuesday, Sekulow addressed the revelation on the Senate floor for the first time.

Trump impeachment trial: Defense ignores Bolton bombshell about Ukraine aid for investigations

"You cannot impeach a president on an unsourced allegation," he said, calling the report "inadmissible" as evidence, though he did not deny the allegation.

In making his point, Sekulow relied heavily on Trump's reaction to the news and commentary from acting chief of staff Mick Mulvaney, whom Sekulow said was not a witness to any talk about investigations between Trump and Zelenskiy.

Trump denied the reports on Monday tweeting that he "NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats."

Trump tweet

Following the Trump defense team's arguments, Republican senators planned to huddle in the Capitol to discuss the next steps in the trial and assess where members of the caucus stood on the question of calling witnesses.

In light of the Bolton revelations, moderate Republicans such as Sens. Mitt Romney of Utah and Susan Collins of Maine expressed more openness to calling for new testimony. The GOP holds a 53-47 majority in the Senate. Democrats need four Republicans to join with them in a vote to call new witnesses.

Senate Majority Leader Mitch McConnell, R-Ky., after the proceedings on Tuesday said a preliminary vote count among senators indicated that the GOP does not have enough votes to block witnesses or additional documents.

Lead impeachment manager Rep. Adam Schiff, D-Calif., made the case for calling Bolton after the day's proceedings, telling reporters that the House tried to subpoena Bolton in its initial investigation but the president's lawyers in a separate court case argued that "the House may not sue in court to compel a witness to testify."

"They come into the Senate, which they refer to as a court, and they say the House should have sued in court to enforce subpoenas on witnesses like John Bolton, and then they go to court and they say the House may not sue in court to compel a witness to testify," Schiff continued. "That is the legal duplicity of the president's team."

But even if Bolton testifies, it remains unlikely that the Senate will vote to convict and remove the president from office.

The Senate will have 16 hours beginning Wednesday to present written questions. Afterward, the Senate will vote on whether to call witnesses or produce additional documents.