Saying Donald Trump has "betrayed our national security" and will do so again, Rep. Adam Schiff used his closing arguments in the president's impeachment trial on Monday to urge the Senate to take a stand against "a man without character."

"We must say enough — enough! He has betrayed our national security, and he will do so again," Schiff, D-Calif., told the Senate. "He has compromised our elections, and he will do so again. You will not change him. You cannot constrain him. He is who he is. Truth matters little to him. What's right matters even less, and decency matters not at all."

"You are decent," he added. "He is not who you are.”

Schiff, the lead House manager in the trial, said Trump has clearly abused his power and would continue to do so unless the Senate stands up to him.

"Can we be confident that he will not continue to try to cheat in [this] very election? Can we be confident that Americans and not foreign powers will get to decide, and that the president will shun any further foreign interference in our Democratic affairs?" Schiff asked. "The short, plain, sad, incontestable answer is no, you can't. You can't trust this president to do the right thing. Not for one minute, not for one election, not for the sake of our country. You just can't. He will not change and you know it."

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"What are the odds if left in office that he will continue trying to cheat? I will tell you: 100 percent," he said. "A man without character or ethical compass will never find his way."

Schiff acknowledged the House managers were unlikely to hit the high bar needed to convict the president, a supermajority of 67 senators. Republicans currently hold the majority with 53 members. Schiff urged them to be among "the Davids who took on Goliath."

"Every single vote, even a single vote by a single member can change the course of history. It is said that a single man or woman of courage makes a majority. Is there one among you who will say ‘enough!’?" Schiff asked.

Another of the House managers, Rep. Jason Crow, warned that if the Senate didn't remove Trump for abuse of power and obstruction of Congress, it would "render him above the law."

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"Impeachment is an extraordinary remedy," said Crow, D-Colo., but "it is in the Constitution for a reason."

House manager Val Demings, D-Fla., said another reason the Senate needs to take action is because the president has been "unapologetic and unrestrained," and will only be more so if the Senate closes his eyes to his misconduct.

"President Trump's constitutional crimes, his crimes against the American people and the nation, remain in progress," Demings said.

Mike Purpura, deputy White House counsel, told the Senate Trump did nothing wrong in his July 25 phone call with Ukrainian President Volodymyr Zelenskiy, and noted comments from Zelenskiy that he never felt any pressure to investigate the Bidens.

Trump lawyer Ken Starr said the House "didn't follow the rules" in their "rushed" impeachment inquiry, and therefore its entire case is fatally flawed. "It's why we don't allow deflated footballs or stealing signs from the field. Rules are rules," he said, referring to cheating scandals involving the NFL's New England Patriots and baseball's Houston Astros.

"It is not liberty and justice for all," Starr said, urging the senators to acquit.

Starr, the special counsel who advocated for Bill Clinton's impeachment, told the senators that if they vote to remove Trump, they'd be telling voters that "your vote in the last election is therefore declared null and void."

White House counsel Pat Cipollone hit a similar note, saying, "At the end of the day, this is an effort to overturn the results of one election and try and interfere in the coming election that begins today in Iowa." The "only appropriate result here is to acquit the president and to leave it to the voters to choose their president," Cipollone said.

Trump's lawyers appeared to be preaching to the Republican choir.

A two-thirds vote is needed to convict a president, and only two members of the Republican majority, Sens. Mitt Romney of Utah and Susan Collins of Maine, sided with Democrats on Friday in their unsuccessful bid to call relevant witnesses.

Some Republican senators, including Lamar Alexander of Tennessee, said there's no need for witnesses because they believed the House managers had already proven their case, and that Trump's actions, while "inappropriate," aren't worth removing him over.

The president appeared to be watching some of the arguments, issuing a tweet with at least one misspelling, "I hope Republicans & the American people realize that the totally partisan Impeachment Hoax is exactly that, a Hoax."

After the closing arguments ended, the trial adjourned until Wednesday, which will allow senators, who were not allowed to speak on the Senate floor during the trial, to deliver remarks about whether they are for or against the articles of impeachment.

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Those speeches are expected to continue until Wednesday at 4 p.m. ET, when a vote on the two articles of impeachment — on abuse of power and obstruction of Congress — is scheduled to take place.

The proceedings are the third presidential impeachment trial in U.S. history, and the first not to feature new testimony from witnesses. Andrew Johnson's trial featured direct testimony from 25 prosecution and 16 defense witnesses, while in Clinton's trial, three witnesses were deposed on video, and snippets of their testimony were played during the trial.

Sen. Chris Van Hollen, D-Md., said he believes the verdict is already in on the Senate, saying the body is "guilty of failure to meet its constitutional obligations.” He said he hopes his Republican colleagues, if they have “any sense of respect for the institution,” would introduce a censure resolution against the president.

Van Hollen said such a move is necessary because Republicans' statements that Trump's actions are inappropriate are like saying “these constitutional abuses were the equivalent of a parking ticket.”