President Trump will go on abusing his office and imperiling elections unless the Senate removes him, House Democrats argued on Friday as they wrapped their opening presentation in Trump's impeachment trial.

Rep. Adam Schiff, D-Calif., warned in some of his strongest language yet that what he called Trump's venality and moral bankruptcy would only grow worse if Congress allows him to remain president after what Democrats say he's committed.

"You don't realize how important character is in the highest office of the land until you don't have it," Schiff said. "There can be little doubt that President Trump will continue to invite foreign interference in our election ... that poses an imminent threat to our democracy."

Democrats told senators they're standing at a crossroads in American history.

If they permit Trump to keep his office — as the majority-Republican chamber is expected to do — they'll forfeit Congress' status as an equal branch of government and effectively greenlight more of what Democrats say are Trump's transgressions.

Trump not only abused his power in the Ukraine affair, Democrats argue. The president's obstruction of Congress in its subsequent investigation is a direct attack on impeachment itself and the checks and balances enshrined in the Constitution.

Even President Richard Nixon complied with Congress' desire to hear from White House officials during Watergate, Nadler said. Trump hasn't.

So a vote to acquit Trump would in effect be a vote surrendering Congress' power to oversee the executive branch and its power of impeachment, Nadler said.

"Historians will mark the date that this Senate allowed this president to break one of our mightiest defenses against tyranny," he warned.

Questions about evidence

Still unresolved within the Senate chamber are the ongoing questions about whether testimony of new witnesses or new documents will be admitted into the proceedings.

Outside the World's Greatest Deliberative Body, however, the story continues to evolve.

One factor is news of a video from April 2018 in which Trump talks with Lev Parnas, an indicted associated of Rudy Giuliani, about firing then-U.S. Ambassador to Ukraine Marie Yovanovitch, according to Parnas' lawyer.

The contents of the tape were first reported by ABC but NPR has not heard the recording.

The White House's spokeswoman and other defenders have observed that Trump has complete power over appointing or removing diplomats.

But the video, if accurate, would undercut earlier defenses by the White House that Trump wasn't aware of what was taking place in the early phase of the Ukraine affair. If the accounts described in the clip are accurate it would suggest Trump not only knew, but he may have been directing events.

More 'crimes'

Democrats argue that Trump and his lieutenants contrived to remove then-Ambassador Marie Yovanovitch because they feared she'd stand in the way of the scheme to pressure Ukraine's government.

If the tape verifies Trump's involvement, it also may dovetail with arguments in the impeachment trial about whether Trump may have committed technical crimes in the Ukraine affair.

The president needn't have broken black-letter law in order to be subject to impeachment, Nadler argued on Thursday, but for the record, Democrats have underscored that his actions in freezing aid for Ukraine did violate the law.

And on Friday, Rep. Val Demings, D-Fla., cited actions against Yovanovitch before and since her removal — including a post on Twitter by Trump even as she was testifying before the House — as what she called textbook witness intimidation by Trump.

"As we all know, witness intimidation is a federal crime," Demings said, calling Trump's comments part of a "reprehensible" pattern of behavior to scare witnesses from coming forward and part of what Democrats call the president's obstruction of Congress.

Trump Team vows to fire back

Trump's attorneys are raring to start their counter-arguments on Saturday.

A source on the president's legal team told reporters that the two to three hours' worth of arguments they're planning will be "coming attractions" for the full days' worth of presentations starting on Monday.

Separately, attorney Jay Sekulow told reporters on Capitol Hill on Friday that he and his compatriots plan to, in effect, impeach Hillary Clinton and Joe Biden.

Sekulow said he intends to argue that Clinton had solicited foreign interference in the 2016 election because Democrats had underwritten the unverified reporting from Russia that came to be known as the Russia dossier.

Trump's team also is expected to underscore the payments that Biden's son Hunter received from the Ukrainian gas company Burisma in 2016 at a time when the elder Biden, as vice president, was leading the U.S. government's policy for Ukraine.

Although the family Biden hasn't been charged with any criminal wrongdoing, that storyline has embarrassed the former vice president as he runs for president this year.

It also has created an opening to talk more broadly about Hunter Biden, whose substance abuse problems and other personal issues are seen by Republicans as a potent line of political attack.

Impeachment is only a quasi-legal process; it's mostly about politics — and Trump's advocates in the Senate chamber have the advantage of being confident about making their case to a mostly friendly jury.

Although Sekulow and other attorneys for Trump have said they'll respond to some of the points that Democrats have made, there are no rules of evidence or other set procedures, as in a legal courtroom, that govern what they say.

They too will talk as much to Americans watching the impeachment proceedings as their hearers in the Senate chamber, as the Democrats have been doing.

"We're going to refute the allegations they've made and we're going to put on an affirmative case as well," Sekulow told reporters.

The bully pulpit

Trump, meanwhile, won't sit still either.

Ad the trial continues, the president is expected to sign a new North American free trade agreement. He is scheduled to host Israeli leaders and may convene an event dedicated to a new Middle East peace proposal. Trump may add new countries to the list of those on which the government applies travel restrictions.

In short, Trump who already has been offering regular commentary about the proceedings on Twitter, has a week's worth of events in store to send the message that — as aides argue — while Democrats waste time, Trump is busy with serious presidential business.

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