Witnesses pointed their fingers at a number of figures close to President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE who could help untangle the web around the administration’s dealings with Ukraine during the public impeachment hearings. But Democrats won’t be hearing from them.

The White House has prevented the president’s chief of staff, his former national security adviser, budget officials and two individuals named as part of the alleged rogue channel behind a push for investigations by Kyiv — his personal attorney and outgoing energy secretary — from testifying before Congress.

Democrats could go to court to try to force the officials to testify, but they don’t want to further delay their inquiry and so have decided to move forward without the additional testimony.

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The stalemate highlights that even as much of the White House’s defense strategy has been criticized as flawed or disjointed, it has succeeded in keeping crucial witnesses from speaking with Congress.

“Clearly, if they were to testify, they would open the White House to new vulnerabilities,” said Doug Heye, a former communications director for the Republican National Committee.

It’s a strategy that does come with risks: Democrats have threatened to draft an article of impeachment accusing the president of obstruction.

“I remind the President that article 3 of the impeachment articles drafted against President Nixon was his refusal to obey the subpoenas of Congress,” House Intelligence Committee Chairman Adam Schiff Adam Bennett SchiffSchiff to subpoena top DHS official, alleges whistleblower deposition is being stonewalled Schiff claims DHS is blocking whistleblower's access to records before testimony GOP lawmakers distance themselves from Trump comments on transfer of power MORE (D-Calif.) said this week at a public hearing with Gordon Sondland Gordon SondlandGOP chairman vows to protect whistleblowers following Vindman retirement over 'bullying' Top Democrat slams Trump's new EU envoy: Not 'a political donor's part-time job' Trump names new EU envoy, filling post left vacant by impeachment witness Sondland MORE, the U.S. ambassador to the European Union.

A parade of officials, many of them career and some political appointees, have testified privately and publicly despite warnings from the White House and offered testimony that generated negative headlines for Trump over several weeks. Among them were three White House officials who this week described concerns about Trump’s July 25 phone call with Ukrainian President Volodymyr Zelensky during which he asked Kyiv for an investigation into former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and his son, Hunter.

The White House has dismissed many of the witnesses as engaging in “hearsay” and Trump has sought distance from them, while taking jabs at their credibility and defending his call with Zelensky.

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Sondland said that he and others worked with Trump’s personal attorney Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE to press for investigations into 2016 election interference and Burisma Holdings, a Ukrainian gas company that employed Hunter Biden, at the “express direction” of the president.

Sondland also testified that he kept top administration officials — including Trump’s chief of staff Mick Mulvaney Mick MulvaneyOn The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security Blockchain trade group names Mick Mulvaney to board Mick Mulvaney to start hedge fund MORE and Secretary of State Mike Pompeo Michael (Mike) Richard PompeoWatchdog confirms State Dept. canceled award for journalist who criticized Trump Trump's push for win with Sudan amps up pressure on Congress Putin nominated for Nobel Peace Prize MORE — abreast of efforts to trade a White House meeting for investigations, furnishing Democrats with emails to bolster his account.

But details surrounding a temporarily hold on $400 million in military aid to Ukraine remain murky. None of the witnesses have offered up clear evidence that the assistance was held so Trump could pressure Ukraine to investigate his 2020 political rival, though a handful have said it was their impression that was the case. Trump has denied a quid pro quo and sought to amplify testimony from Sondland where he described a September phone call during which the president said he wanted "nothing" from Ukraine.

“I think the White House believes that it’s white noise,” said one source close to the White House. “There’s nothing new there, there’s no smoking gun.”

Mulvaney acknowledged in a press briefing last month that the administration held up the aid because Trump wanted to investigate a conspiracy theory about the DNC server, but quickly pulled back his remarks. The acting chief of staff evaded a subpoena compelling his testimony this month.

Absent a major shift, Democrats won’t have the opportunity to question Giuliani about his efforts on Ukraine; they won’t hear from former national security adviser John Bolton John BoltonJudge appears skeptical of Bolton's defense of publishing book without White House approval Maximum pressure is keeping US troops in Iraq and Syria Woodward book trails Bolton, Mary Trump in first-week sales MORE about his alleged concerns that the Ukraine effort amounted to “drug deal”; nor will they grill White House lawyer John Eisenberg about the decision to move a transcript of the Ukraine call to a server reserved for highly classified material.

Vice President Pence, who along with Giuliani and Pompeo has evaded subpoenas for documents, was also named as having knowledge about the push for investigations. Democrats have not requested testimony from the three individuals, who would be unlikely to comply if summoned.

Still, Democrats are pressing forward having gleaned what they view as evidence Trump engaged in bribery and other offenses.

Over the Thanksgiving break, the House Intelligence Committee is expected to start drafting a report detailing the Trump-Ukraine scandal that draws on witness testimony.

The House Judiciary Committee will begin drafting articles of impeachment in December; it’s unclear whether they will hold their own open hearings before the articles are put to a vote, or whether the package will ultimately include an article accusing Trump of obstructing the inquiry.

“I’m not sure that one more article on top of the others that Democrats are already certain to send up makes a big difference,” said one Republican strategist. “What we learned this week is that both sides are sprinting toward their respective corners are hard as they possibly can.”

White House aides have acknowledged they’re prepared for Trump to be impeached by the Democrat-controlled House. On Friday, Trump embraced the idea of a full trial in the Senate, while suggesting Democrats were “crazy” to vote on impeachment and asserting his call with Zelensky was “totally appropriate.”

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While the GOP-controlled Senate is more favorable territory for Trump, an impeachment trial threatens to distract from the president’s agenda as the controversy bleeds further into his 2020 reelection campaign.

Still, Republican strategists say impeachment has yet to adversely affect Trump, pointing to his steady approval rating and recent polls showing that support for impeachment waning particularly among independents.

“You’re not seeing members of Congress change their minds. You’re not seeing voters change their minds,” said Heye. “The simple reality is after what should have been a terrible week for the White House, the number hasn’t changed.”