WASHINGTON  — Democratic House prosecutors are launching their final arguments Friday at Donald Trump’s impeachment trial after an impassioned plea to senators to convict him because in the U.S. “right matters.”

As Democrats press their case before skeptical Republican senators for the third day, the president’s legal team is preparing its defense, expected to start Saturday. Trump, eyes on the audience beyond the Senate chamber, bemoaned the schedule in a morning 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. Trump is accused of abuse of power and obstruction of Congress in seeking politically motivated probes from Ukraine of political foe Joe Biden and Biden’s son while holding back congressionally approved military aid as leverage.

Rep. Adam Schiff, the Democratic chairman of the House Intelligence Committee, made an emotional plea late Thursday 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.”

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 the investigations while withholding aid from a U.S. ally 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.

With Chief Justice John Roberts presiding, Democrats argued on Thursday 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 attorney Rudy Giuliani.

They argued that Trump’s abuse was for his own personal political 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.

“That’s what Donald Trump wanted investigated or announced — this completely bogus Kremlin-pushed conspiracy theory,” Schiff declared.

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 debunked theories of what nation was guilty of interference 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. Pressed by one of the TV hosts as to what that evidence was, Giuliani claimed he had “witnesses” willing to speak on the record next week.

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

At one point, they showed video of a younger Lindsey Graham, then a South Carolina congressman and now a GOP senator allied with Trump, arguing during Bill Clinton’s 1999 impeachment that no crime was needed for impeaching a president. Trump’s defense team is now arguing that the impeachment articles against him are invalid because they do not allege he committed a specific crime.

The president’s defenders’ turn will come Saturday.

“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.

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 top Senate Democrat, Chuck Schumer, acknowledged that many senators “really don’t want to be here.”

But Schumer said Schiff has been outlining a compelling case that many Republicans are hearing for only the first time. He contended they can’t help but be “glued” to his testimony.

“No president has ever used his office to compel a foreign nation to help him cheat in our elections,” Rep. Jerrold Nadler of New York, the chairman of the House Judiciary Committee, told the senators. He said the nation’s founders would be shocked. “The president’s conduct is wrong. It is illegal. It is dangerous.”

Senators were permitted Thursday to review supplemental testimony submitted by an aide to Vice President Mike Pence, Jennifer Williams, who was among those who had concerns about Trump’s actions. Democrats said the testimony, which is classified, bolsters their impeachment case. A lawyer for Williams declined to comment.

Holding the room’s attention has been difficult for the Democrats, but senators seemed to pay closer mind to Schiff’s testimony that grew dramatic.

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.