(CNN) The big news closing the week was the unveiling of President Donald Trump's impeachment defense team and the release of more documents related to Lev Parnas, the indicted associate of Rudy Giuliani. And we'll have more on that in a moment.

The issue of whether to hear witnesses and receive new evidence is expected to dominate portions of the Senate trial

So it's worth noting, as we prepare for the trial to begin in earnest Tuesday, how much we've learned about the Ukraine scandal even in the month since Trump was impeached December 18.

John Bolton offered to testify with or without blessing from a court if he's subpoenaed in the Senate.

Parnas turned on Trump and turned over documents about his interactions with Giuliani regarding Ukraine, along with the disturbing effort to oust then-US Ambassador Marie Yovanovitch, and discussed his interactions with Trump in interviews.

The Government Accountability Office, Congress' nonpartisan investigative arm, said the Trump administration's effort to freeze the aid to Ukraine broke the law, since Congress had already appropriated the funds.

That's a lot of new information related to the impeachment effort. Republicans in the Senate want to argue that the House should have figured all of this out before impeaching Trump. There is certainly an argument that the House, in its effort to move quickly -- members argued that Trump was attempting to impact the 2020 election, so they were trying to stop a high crime in progress -- brought the case to trial too early.

And certainly there are many facts that remain unknown, such as what additional documents at the White House Office of Management and Budget, the State Department and the Pentagon would say about the frozen aid.

The truth will be a long time coming

But the argument by many Republican senators that they shouldn't hear new information appears designed to ignore key new facts. That will aid Democrats' argument that the Senate trial will end up covering up Trump's alleged misdeeds. But it's also true that the speed Democrats insisted on means we'll be learning new facts about Trump and Ukraine long after his likely acquittal by the majority trying to protect him in the Senate.

Impeachment Watch Podcast: David Chalian talked with Sarah Wire, a congressional reporter for the Los Angeles Times and the chair of the Standing Committee of Correspondents. They spent time discussing the unprecedented restrictions for the press covering impeachment.

Trump's defense team

President Trump unveiled his impeachment defense team Friday.

He chose some TV and historical personalities, including Alan Dershowitz, the Harvard professor, Kenneth Starr, the former independent counsel famous for his pursuit of Bill Clinton, which resulted in that president's impeachment, and Robert Ray, Starr's successor in that role.

Cipollone and Sekulow will take the lead

Dershowitz, Starr and Ray are expected to join a legal team headed by White House counsel Pat Cipollone and outside attorney Jay Sekulow, who are expected to deliver statements on the President's behalf on the Senate floor. Former Florida Attorney General Pam Bondi, Trump's longtime personal counsel Jane Raskin and attorney Eric Herschmann will also supplement the President's impeachment legal team, a person familiar with the matter said. All are expected to have speaking roles.

Part-time defender

Dershowitz qualified his participation when he told Mediaite that it would be "overstating it" to call himself a member of Trump's legal team despite the fact that he is expected to participate in the Senate trial on the President's behalf.

"I was asked to present the constitutional argument that I would have presented had Hillary Clinton been elected and had she been impeached," Dershowitz told the website, adding: "I was asked to present my constitutional argument against impeachment. I will be there for one hour, basically, presenting my argument. But I'm not a full-fledged member of the defense team in any realistic sense of that term."

Dershowitz isn't 100% on Trump's team and Trump used to say very unflattering things about Starr.

House supporters didn't make the cut

Left off Trump's defense team were his supporters in the House. Senators had counseled him to make a clean break from the "circus" of impeachment there.

More new Lev Parnas developments

House impeachment investigators released more new documents from Parnas on Friday evening that suggest some kind of surveillance, involving Connecticut congressional candidate Robert Hyde, of Yovanovitch, and additional contacts between Parnas and an aide to Republican Rep. Devin Nunes of California. Here's what we learned from them.

In his interview with CNN, Parnas told Anderson Cooper that Trump's efforts to pressure the Ukrainian government had included an attempted quid pro quo with the country's previous President, Petro Poroshenko.

Revealing what he claims is a previously undisclosed meeting, Parnas said he had met Poroshenko in early 2019, during the final weeks of Ukraine's presidential campaign, and tried to broker a political arrangement on behalf of Trump and Giuliani.

According to Parnas, Trump offered to endorse Poroshenko if he announced an investigation into former Vice President Joe Biden. "If he would make the announcement ... Trump would either invite him to the White House or make a statement for him, but basically would start supporting him for president," Parnas said.

But the deal fell flat. Poroshenko didn't announce any investigations, and a few months later, he was soundly defeated by Zelensky.

More Mueller documents released to CNN and BuzzFeed

One tidbit: Mueller investigated a controversial change to the Republican Party's platform during the 2016 convention. His report said Trump campaign officials had blocked a provision calling for the US to provide lethal weapons to the Ukrainian military for its war against Russian-backed proxies.

It said the investigation had been unable to establish that the change was made "at the behest of candidate Trump or Russia."

While the report doesn't say whether Manafort was involved, Page said he "suspected Manafort may be behind it."

Trump campaign aides also removed language calling for the US to financially support Ukraine's budding anti-corruption bureau.

Giuliani once ran the office now investigating him

Exposure to Trump transforms people. Or it reveals them.

Sen. Lindsey Graham, for instance, was Sen. John McCain's sidekick. Now the South Carolina Republican is Trump's defender.

The evolution is most complete in Giuliani. He was America's mayor. Now he's heir to Michael Cohen, Trump's personal attorney, fixing things for the boss and doing his own side deals.

It centers on the fact that Giuliani was once the crime-fighting US attorney based in Manhattan.

He used to run the office, but now he's being investigated by it and has referred to the prosecutors as "assholes."

"He was like all of us. He's imperfect, but he was a very good and inspiring United States attorney who made major prosecutions," said Paul Shechtman, a partner at the law firm Bracewell LLP who worked under Giuliani as a federal prosecutor, including as head of the office's appeals division.

"For those of us who worked for him, the fact that our old office is investigating him is a dark day," Shechtman said.

Trial schedule

Monday through Saturday, beginning at 1 p.m. ET

If the Senate follows the model from President Bill Clinton's impeachment trial -- as Majority Leader Mitch McConnell has said he wants to do -- each side would have not more than 24 hours to do opening arguments. After that there would 16 hours for senators to ask questions, which would be submitted in writing.

Doing the math

Opening arguments could take about 10 days and questions might take three if the prosecution and defense use all their time.

Only then would they turn to the issue of witnesses.

Pence compared Trump's impeachment to Andrew Johnson's. He might not want to do that.

Vice President Mike Pence urged Senate Democrats to break ranks and "stand up against" the articles of impeachment in a Wall Street Journal op-ed comparing Trump's Senate trial to President Andrew Johnson's impeachment trial in 1868.

It's a flawed comparison from the standpoint that Johnson is not viewed very kindly by history. His efforts to blunt Reconstruction after the Civil War helped further oppress African Americans.

Plus, the senator Pence lionizes for saving Johnson voted against the majority in the Senate. Trump's Republicans enjoy a majority in the Senate. I've written about this.

What are we doing here?

The President has invited foreign powers to interfere in the US presidential election. Democrats impeached him for it. A Senate trial is next. It is a crossroads for the American system of government as the President tries to change what's acceptable for US politicians. This newsletter will focus on this consequential moment in US history.