On a letter to Cipollone
, House managers argue that Cipollone has "detailed knowledge of the facts" about Trump's relations with Ukraine, that he "played an instrumental role" in implementing Trump's directive to block witnesses and testimonies, and that he should therefore disclose what do you know so that "The Senate and the Chief Justice can be informed about possible ethical issues, conflicts or prejudices".
Democrats alone do not have the power to force Cipollone to do anything. If they believe he has critical information first hand, they may press for a vote on deposition or request for public testimony, but that would require Republican support.
Still, the move was the latest in an escalation between House Democrats and the White House. Trump has been saying
Democratic Congressman Adam Schiff, who leads House managers and oversaw the investigation on the House Intelligence Committee, illegally
coordinated with the Ukrainian whistleblower and should be required to testify at the trial.
The Democrats' letter said the Cipollone situation "threatens to undermine the integrity of the pending trial", increasing its criticism of the Republican-led process that they labeled "cover-up."
Deputy Jerry Nadler, one of the Democratic managers and chairman of the House Judiciary Committee, said Tuesday that Cipollone should refuse Senate procedures.
The fight for witnesses on both sides has been simmering for weeks.
The summary of the President's judgment, which was submitted to the Senate on Monday
and co-written by Cipollone, he also accused Schiff of being an "interested witness" because of the whistleblower, and the hearings he supervised were therefore "fatally flawed". These hearings with key witnesses found strong evidence linking Trump to Ukraine's pressure campaign.
It is not true that Schiff violated the law, and Trump exaggerated Schiff's connections with the whistleblower, who spoke to members of the Schiff committee team
before filing the complaint. That complaint raised the alarm about Trump's July 25 connection with Ukrainian President Volodymyr Zelensky, where he called for an investigation into former Vice President Joe Biden.
CNN had previously reported that Senate majority leader Mitch McConnell preferred a quick trial without witnesses on either side, as opposed to the protracted process that Trump was calling for, where his defense lawyers could try to summon a witness stand, including Schiff and potentially Biden. A majority vote is required to approve any new subpoena by witness.
White House and Senate Republicans plan to defend the role of Cipollone, officials involved in the discussions told CNN.
"House Democrats are trying to remove one of the president's strongest lawyers before he starts," said White House legislative director Eric Ueland. "They will not be successful."
Since Trump became president, the lawyers around him have been drawn to his scandals.
Former White House adviser Don McGahn was one of the main witnesses to the investigation in Russia and provided Special Counsel Robert Mueller significant evidence that Trump obstructed justice
. Mueller declined to offer recommendations on whether Trump should be accused of obstruction, and Justice Department guidelines say that an incumbent president cannot be indicted.
Trump's former personal lawyer, Michael Cohen, has implicated Trump in campaign finance crimes for his role in secret money payments sent to two women who have alleged cases with Trump. Cohen is now serving three years in prison
for these and other crimes. Trump denies the issues.
And Trump's lawyer Rudy Giuliani played a leading role in the effort to pressure Ukraine to announce Biden's investigations – the conduct that led directly to Trump's impeachment. Federal prosecutors are investigating
Giuliani's relationship with two Soviet-born businessmen who helped him with the Ukrainian scheme and now face campaign financial charges on their own.
CNN's Haley Byrd and Manu Raju contributed to this article.