WASHINGTON (AP) — Democratic House prosecutors launched their final arguments Friday at Donald Trump's impeachment trial arguing the president will persist in abusing the power of his office ahead of the 2020 election unless Congress intervenes to remove him from office.

"He is who he is," Rep. Adam Schiff, the chairman of the House Intelligence Committee, told senators, accusing Trump of 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 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."

As Democrats pressed their case before skeptical Republican senators for a third day, the president's legal team was preparing for his defense, expected to start 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."

The Senate jurors faced another long day Friday armed with pens and paper — and, for Republicans, the gift of fidget spinners — for the historic trial.

The president 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 political foe Biden and Biden's son 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.

Republicans have defended Trump's actions as appropriate and are casting the process as a politically motivated effort to weaken him in his reelection campaign. Republicans hold a 53-47 majority in the Senate, and acquittal is considered likely.

The Senate is heading next week toward a pivotal vote on Democratic demands for 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. He said he doesn't want to hear from Bolton or the Bidens.

With Chief Justice John Roberts presiding, Friday's arguments opened with Democrats wrapping up their presentation on the first article of impeachment, abuse of power, before turning to the second, obstruction of Congress.

The Democrats relied on the words of the late Republican Sen. John McCain to explain to senators why Trump's decision to block the military aid to Ukraine was so "disturbing," as Schiff put it.

It wasn't just a policy dispute, Schiff argued, but "one hell of a Russian intelligence coup" as Trump chased "kooky" theories about Ukraine pushed by Trump lawyer Rudy Giuliani that benefited Vladimir Putin at U.S. expense.

"This is Trump first. Not America first," Schiff declared.

On Thursday, the Democrats argued that Trump's motives were apparent, that he abused power like no other president in history, swept up by a "completely bogus" Ukraine theory pushed by Giuliani.

Schiff made an emotional plea for senators to consider what was at stake.

"Let me tell you something. If right doesn't matter, it doesn't matter how good the Constitution is," Schiff told a pin-drop-quiet room. "If you find him guilty you must find that he should be removed. Because right matters."

Democrats argued that Trump's abuse was for his own benefit ahead of the 2020 election, even as the nation's top FBI and national security officials were publicly warning off the theory that it was Ukraine, not Russia, that interfered in the 2016 election.

The Democrats' challenge is clear as they try to convince not just fidgety senators but an American public divided over the Republican president in an election year.

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.

After both sides have concluded their arguments next week, senators will face the question of whether to call witnesses to testify. But that issue has seemed all but settled. Republicans rejected Democratic efforts to get Trump aides, including Bolton and Mulvaney, to testify in back-to-back votes earlier this week.

As for the Ukraine connections, evidence 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 the probe of the 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.

Democrats, in their Senate prosecution, seemed to be anticipating arguments expected from the president's defenders.

"We will be putting on a vigorous defense of both facts, rebutting what they said," and the Constitution, said attorney Jay Sekulow.

During their presentations, Democrats have been summarizing much of the evidence and testimony already presented during televised House impeachment hearings . Holding the room has been difficult.

Sen. Roy Blunt, R-Mo., said the Democrats were putting forward "admirable presentations." But he said, "There's just not much new here."

Sen. John Barrasso, R-Wyo., said it seemed like "Groundhog Day in the Senate."

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.