House Democrats have already raised concerns about Cipollone’s role in the Ukraine saga, portraying him as a fact witness for both of the impeachment articles against the president. And Friday's news is likely to renew that scrutiny.

In a letter to Cipollone last week, the House impeachment managers asked him to disclose “all facts and information as to which you have first-hand knowledge that will be at issue in connection with evidence you present or arguments you make in your role as the president’s legal advocate.” They also said such information could present ethical and conflict-of-interest issues.

Team Trump has long shrugged off the concerns about Cipollone. “Nonsense,” Jay Sekulow, the president’s longest-serving personal lawyer, replied after the House impeachment managers’ letter at the onset of the Senate proceedings.

Indeed, Cipollone has been at the center of the Trump trial defense strategy alongside his top deputies — Patrick Philbin and Michael Purpura — and Sekulow.

Cipollone's inclusion has troubled Democrats, but they are not fully united on what should be done about it.

“I think there are issues,” Sen. Chris Van Hollen (D-Md.) told POLITICO on Monday just minutes before the president’s lawyers launched into their first full-bore defense of their case. “He clearly is a fact witness to some of these events and has direct personal knowledge about allegations that are directly relevant to the charges.”

Sen. Richard Blumenthal, a frequent Trump critic, said on Monday he was not ready to call for Cipollone to remove himself from the Trump defense team.

“Disqualification is a very major remedy," the Connecticut Democrat said in an interview. "So I wouldn't leap to that conclusion at this point."

But Blumenthal, a former state attorney general, said that questions about Cipollone’s role in a trial where he’s a fact witness remained a frequent topic of conversation in his own circles.

“You know, I can tell you, quite honestly, lawyers have been calling and saying, ‘How does Cipollone explain his representations to the United States Senate, in a court, of failure to disclose the knowledge he had?’”

Blumenthal noted that any judge would raise such questions “in a normal courtroom setting.” But an impeachment trial, with Chief Justice John Roberts serving as the presiding officer, is far from a typical case.

“Now we're not in a normal trial," Blumenthal said. "But lawyers are reacting to say, ‘What's going on here? These lawyers are part of the activities directly at issue."

Rep. Adam Schiff (D-Calif.), the House’s lead impeachment manager, mentioned the new revelation at the beginning of Friday’s session of the Senate’s impeachment trial as he continued to make the case that senators should vote in favor of calling new witnesses, such as Bolton.

“Here you have the president saying John Bolton is not telling the truth. Let’s find out. Let’s put John Bolton under oath. A trial is supposed to be a quest for the truth. Let’s not fear what we will learn,” Schiff said. “As Mr. Cipollone said, let's make sure all the facts come out.”

The reported meeting falls just before Giuliani wrote directly to Zelensky, asking for a meeting in which he intended to make an undisclosed “request” with the “full knowledge and consent” of the president.

“In my capacity as personal counsel to President Trump and with his knowledge and consent, I request a meeting with you on this upcoming Monday, May 13th or Tuesday, May 14th,” Giuliani wrote in the May 10 letter, which was turned over to House investigators by Lev Parnas, an indicted former associate of Giuliani.

A month later, Trump inquired about — and ultimately froze — military aid to Ukraine. On July 25, Trump spoke to Zelensky and pressed him to investigate his Democratic adversaries, including Biden, who had announced his presidential campaign in late April.