Senators on Wednesday night agreed to admit a classified document from an aide to Vice President Pence into the impeachment trial following closed-door deliberations.

The one-page document relates to a phone call that took place between Pence and Ukrainian President Volodymyr Zelensky a week before Zelensky met with President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE last fall at the United Nations.

This latest development is a win for House Democrats who have unsuccessfully pressed the White House to declassify the document, which Pence aide Jennifer Williams submitted to the House in late November to supplement her public testimony earlier that month.

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House managers who function as prosecutors in Trump’s Senate trial continued to criticize the White House’s refusal to declassify the evidence and urged senators on Wednesday to review its contents.

“I've read that testimony. I will just say that a cover-up is not a proper reason to classify a document,” said Rep. Zoe Lofgren Zoe Ellen LofgrenTop Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence DHS opens probe into allegations at Georgia ICE facility House passes legislation to boost election security research MORE (D-Calif.), one of the managers. “In case the White House needs a reminder, it's improper to keep something classified just to avoid embarrassment or to conceal wrongdoing.”

Williams’s evidence may be accessed by senators in a classified setting but will not be made public, according to the terms of the closed-door agreement announced late Wednesday by Supreme Court Chief Justice John Roberts, who is presiding over the trial.

A number of Senate Democrats on Thursday morning were seen at the Capitol building entering a Sensitive Compartmented Information Facility, or SCIF, to review the document. They included Sens. Richard Blumenthal (D-Conn.) and Michael Bennet Michael Farrand BennetOVERNIGHT ENERGY: House Democrats tee up vote on climate-focused energy bill next week | EPA reappoints controversial leader to air quality advisory committee | Coronavirus creates delay in Pentagon research for alternative to 'forever chemicals' Senate Democrats demand White House fire controversial head of public lands agency Next crisis, keep people working and give them raises MORE (D-Colo.), who is running for president.

Emerging from the SCIF, Blumenthal called for the Williams document to be declassified.

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"There's no reason that it should be kept classified. It should be made public, regardless of which side it helps. The American people should judge," Blumenthal, a former Connecticut attorney general, told reporters.

"And all those other documents, notes of conversations, that have been the topic of testimony –– internal communications, memoranda, messages –– all of them should be made available."

In her public testimony before the House Intelligence Committee in November, Williams, a special adviser on Europe and Russia, described her alarm while listening in on the July 25 phone call between Trump and Zelensky that is at the heart of the impeachment proceedings.

One of the two impeachment articles against Trump accuses him of abuse of power, centering on the withholding of nearly $400 million in U.S. military and security assistance to Ukraine last year amid efforts to push the country to launch investigations into Trump's political rivals. Trump allies have dismissed that article, noting that the aid was eventually transmitted.

While the White House readout of the July 25 phone call does not specifically identify the company that would figure into the investigation, Williams told impeachment investigators her handwritten notes reflect that Zelensky said "Burisma," a Ukrainian energy company where the son of Democratic presidential candidate Joe Biden Joe BidenSenate Republicans face tough decision on replacing Ginsburg What Senate Republicans have said about election-year Supreme Court vacancies Biden says Ginsburg successor should be picked by candidate who wins on Nov. 3 MORE was once a board member.

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Williams also said Trump’s mention of specific investigations into political rivals was "unusual and inappropriate" and "shed some light on possible other motivations behind a security assistance hold."

A week after her public testimony, with her recollection refreshed, Williams submitted a classified document to the House describing a September phone call between Pence and Zelensky.

A Democratic official working on the impeachment trial said the supplemental testimony will allow the Senate “to see further corroborative evidence as it considers articles of impeachment.”

– Scott Wong contributed

Updated: 1:53 p.m.