WASHINGTON  — Closing out their case, House Democrats warned Friday in Donald Trump’s impeachment trial that the president will persist in abusing his power and endangering American democracy unless Congress intervenes to remove him before the 2020 election.

They then implored Republican senators to allow new testimony before rendering a final verdict.

“Give America a fair trial,” said Rep. Adam Schiff, the lead Democratic impeachment manager. “She’s worth it.”

Schiff delivered Democrats’ final remarks in the Senate trial after three days of methodical and impassioned arguments detailing charges that Trump abused power by asking Ukraine for politically motivated probes of political rivals, then obstructed Congress’ investigation into the matter. The president’s lawyers get their first chance to defend him Saturday, and are expected to argue he acted appropriately.

The opening arguments appear to have done nothing to shake Republicans’ support for Trump or persuade enough centrist GOP lawmakers to call for new witnesses, including Trump’s former national security adviser John Bolton. In his final appeal to lawmakers and a divided nation, Schiff argued that a guilty verdict in the Senate is the only remedy left to curb what he called the “’imminent threat” posed to the nation by Trump’s unconstitutional impulses.

“He is who he is,” Schiff declared. “You know it’s not going to stop. ... It’s not going to stop unless the Congress does something about it.”

The moment of history was apparent, only the third impeachment trial of a U.S. president, as were the partisan views of the Trump presidency and the effort to end it.

When Schiff cited a news story with someone close to Trump saying any Republican voting with Democrats would have their “head on a pike,” GOP senators in the chamber began murmuring, “That’s not true.”

The House impeached Trump last month, accusing him of abusing his office by asking Ukraine for politically motivated probes of Biden and other matters while withholding military aid from a U.S. ally that was at war with bordering Russia. A second article of impeachment accuses him of obstructing Congress by refusing to turn over documents or allow officials to testify in the House ensuing probe.

Said Trump attorney Jay Sekulow, “We’re going to rebut and refute, and we’re going to put on an affirmative case tomorrow.”

Republicans are defending Trump’s actions as appropriate and are casting the impeachment trial as a politically motivated effort to weaken him in his reelection campaign. Republicans hold a 53-47 majority in the Senate, and eventual acquittal is considered likely.

Before that, senators will make a critical decision next week on Democratic demands to hear testimony from top Trump aides, including Bolton and acting chief of staff Mick Mulvaney, who refused to appear before the House. It would take four Republican senators to join the Democratic minority to seek witnesses, and so far the numbers appear lacking.

“This needs to end,” said Sen. Lindsey Graham, R-S.C., a Trump confidant.

With Chief Justice John Roberts presiding, Friday’s session opened with an overarching case from Democrats that Trump’s actions with Ukraine were not unique but part of a pattern of “destructive behavior” now threatening the core foundations of American democracy.

Schiff told the senators that Trump has shown repeatedly that he is willing to put his personal political interests above those of the country he is sworn to protect.

The evidence shows, he said, that Trump bucked the advice of his own national security apparatus to chase “kooky” theories about Ukraine pushed by lawyer Rudy Giuliani, resulting in “one hell of a Russian intelligence coup” that benefited Vladimir Putin at U.S. expense.

This was not simply a foreign policy dispute, Schiff argued, but a breech of long-held American values for Trump to leverage an ally — in this case Ukraine, a struggling democracy facing down Russian troops — for the investigations he wanted ahead of 2020.

When the House started investigating his actions, Democrats said, Trump blatantly obstructed the probe. Even then-President Richard Nixon, they argued, better understood the need to comply with Congress in some of its oversight requests.

Drawing on historical figures, from the Founding Fathers to the late GOP Sen. John McCain and the fictional Atticus Finch, Schiff made his arguments emphatically personal.

“The next time, it just may be you,” he said, pointing at one senator after another. “Do you think for a moment that if he felt it was in his interest, he wouldn’t ask you to be investigated?”

The impeachment trial is set against the backdrop of the 2020 election, as voters assess Trump’s presidency and his run for a second term. Four senators who are Democratic presidential candidates are off the campaign trail, seated as jurors.

A new poll from The Associated Press-NORC Center for Public Affairs Research showed the public slightly more likely to say the Senate should convict and remove Trump from office than to say it should not, 45% to 40%. But a sizable percentage, 14%, said they didn’t know enough to have an opinion.

One issue with wide agreement: Trump should allow top aides to appear as witnesses at the trial. About 7 in 10 respondents said so, including majorities of Republicans and Democrats, according to the poll.

No president has ever been removed by the Senate, neither Andrew Johnson in 1868 nor Bill Clinton in 1999. Nixon left office before a House vote that was likely to impeach him.

The House mounted its Trump case after a government whistleblower complained about his July 2019 call with Ukraine. The House relied on testimony from current and former national security officials and diplomats, many who defied White House instructions not to appear.

Evidence presented in the House probe has shown that Trump, with Giuliani, pursued investigations of Biden and his son, Hunter, who served on a Ukrainian gas company’s board, and sought a probe of a debunked theory that Ukraine interfered in the 2016 U.S. election.

It’s a story line many in the president’s camp are still pushing. Giuliani, in an appearance Friday on “Fox & Friends,” insisted he would present evidence on his new podcast.

At close, Schiff predicted the Trump team will try to distract senators from the case, in part by lodging personal attacks against all the House prosecutors. He reminded senators what is at stake and read the articles of impeachment one more time.