Washington • House Democrats warned as they closed their arguments Friday in Donald Trump's impeachment trial that the president will persist in abusing his power and endanger American democracy unless Congress intervenes to remove him before the 2020 election.

“He is who he is," declared Rep. Adam Schiff, the chairman of the House Intelligence Committee. He told the senators listening as jurors that Trump putting the U.S-Ukraine relationship on the line in a way that benefited Russia just so he could take a political“cheap shot” at Democratic foe Joe Biden.

“You cannot leave a man like that in office," Schiff said. “You know it's not going to stop. It's not going to stop unless the Congress does something about it.”

Trump is is being tried in the Senate after the House impeached him 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. The second article of impeachment accuses him of obstructing Congress by refusing to turn over documents or allow officials to testify in the House probe.

As Democrats finished their third day before skeptical Republican senators, Trump's legal team prepared to start his defense, expected on Saturday. Trump, eyes on the audience beyond the Senate chamber, bemoaned the schedule in a tweet, saying “looks like my lawyers will be forced to start on Saturday, which is called Death Valley in T.V.”

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 more testimony from top Trump aides, including acting chief of staff Mick Mulvaney and former national security adviser John Bolton 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 a sweeping and impassioned argument 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 is not simply a foreign policy dispute, Schiff argued, but a breech of long-held American values to leverage an ally — in this case Ukraine, a struggling democracy facing down Russian troops at its border — for the investigation of Biden that Trump wanted ahead of 2020.

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 senators though, appear as deeply divided as the nation, with Democrats ready to vote to convict the president and Republicans poised to acquit.

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.

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 of “collusion going on in Ukraine to fix the 2016 election in favor of Hillary" Clinton.

The impeachment trial is set against the backdrop of the 2020 election. Four senators who are Democratic presidential candidates are off the campaign trail, seated as jurors.

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Associated Press writers Mary Clare Jalonick, Alan Fram, Andrew Taylor, Laurie Kellman, Matthew Daly and Padmananda Rama contributed to this report.