President Trump's defense team on Monday will continue its arguments in the Senate impeachment trial, expected to maintain that the president was legally justified in freezing military assistance to Ukraine and that the case against Trump presented by Democrats does not clear the bar of an impeachable offense.

The arguments come a day after a report by the New York Times that Trump directly told his former national security adviser John Bolton that he would hold up aid to Ukraine until the country launched investigations into his political rivals.

WATCH LIVE: Trump's Impeachment Trial Resumes

The military assistance and the desired investigations are at the heart of the impeachment proceedings. Democrats say Trump's actions constitute a clear case of abuse of power, with Trump placing his personal interests over the country's. The legal team representing Trump in the Senate trial argues that the president had justifiable concern about corruption in Ukraine.

The aid was ultimately released without the probes.

The constitutional standard

Lawyers for the president offered a brief glimpse of their defense Saturday, minimizing the evidence House investigators gathered before the Democratic-led chamber impeached Trump for abuse of power and obstruction of Congress.

Pat Cipollone, the White House counsel, claimed Democrats' push to remove Trump from office is aimed at overturning the result of the 2016 election, and "tearing up [voters'] ballots" months before the 2020 election.

After a day off Sunday, Trump's defense lawyers will resume their impeachment defense at 1 p.m. ET. Watch the trial live here when it begins.

On Sunday, Alan Dershowitz, another member of the defense team, said on Fox News Sunday that the Democratic-led prosecution does not have a case that passes constitutional muster.

"They completely failed to meet that high constitutional standard, and therefore it would be unconstitutional to remove a president based on the allegations that were made against him," Dershowitz said. "They imposed very stringent criteria for impeachment that haven't been met in this case," citing the founders' standard for impeachment, which is "treason, bribery and other high crimes and misdemeanors."

In December, the House passed two articles of impeachment against Trump, abuse of power and obstruction of Congress. The vote for impeachment followed hours of testimony, in private and in public, with more than a dozen witnesses during the House impeachment inquiry.

Trump's legal team is also expected to take aim at the president's potential political opponent, Joe Biden, and his son Hunter, making the case that Trump had good reason to want Ukrainian investigators to launch criminal probes into the activities of the Bidens in Ukraine. (While Joe Biden was vice president, Hunter Biden took a position as board member of a gas company in Ukraine.)

The full-throated defense of Trump comes after the nonpartisan Government Accountability Office declared that the president broke the law in ordering a hold on nearly $400 million in security assistance to Ukraine.

Because the Trump administration refused to participate in the House impeachment inquiry, the president's defense in the Senate is the first time Trump's team will present a lengthy rebuttal to the charges against him.

The push for witnesses

Over three days of arguments last week, House impeachment managers outlined their case that Trump enlisted a foreign power to help him cheat in the 2020 election and then has tried to cover it up. They've said that the president's conduct is the "worst nightmare" of the nation's framers.

The Trump legal team is facing a mostly sympathetic group of jurors in the Republican-controlled Senate. An acquittal on the two articles of impeachment is all but guaranteed, since the Democratic caucus would need 20 GOP members' support in order to have the two-thirds majority needed to convict and remove the president.

More up in the air, however, is whether Democrats will be able to recruit enough Republicans in order to call witnesses for the trial. That vote has a lower threshold than the one required to remove the president from office. At least four GOP senators would have to cross party lines in order to call witnesses or subpoena documents.

In light of the New York Times report Sunday about a draft of Bolton's forthcoming book, Democrats were quick to reiterate that Bolton should testify.

"The Senate trial must seek the full truth and Mr. Bolton has vital information to provide," the House impeachment managers said in a statement.

NPR has not seen a draft of the manuscript and cannot vouch for the accuracy of the report on Trump's comments to the former national security adviser.

House Democrats had asked Bolton to testify during the impeachment inquiry, but did not issue him a subpoena. The White House had ordered senior officials to not testify.

Any vote on witnesses and new evidence would come after the defense team rests (it has up to 24 hours over three days), and after senators have a chance to ask questions in writing of both House prosecutors and Trump's legal team. The questions will be read out loud by Chief Justice of the U.S. John Roberts, who's presiding over the trial.

Trump weighs in

While Trump has not attended the Senate proceedings, and is not expected to, the president has been disparaging Democrats leading the prosecution.

On Sunday, Trump tweeted that lead impeachment manager, Rep. Adam Schiff, D-Calif., "has not paid the price, yet, for what he had done to our country!"

Speaking on NBC's Meet the Press Sunday, Schiff said Trump is "wrathful and vindictive" and he believes the president's tweet was "intended to be" a threat.

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