David KnowlesEditor•Schiff says House committee will investigate allegations that communications were shielded by WH House Democrats are said to be eyeing a fast-paced impeachment inquiry into President Trump’s dealings with the president of Ukraine, a process that could bring a resolution to the floor for a vote by the end of November.But even a narrow focus could throw a spotlight on a huge cast of administration officials directly or peripherally involved in Trump’s efforts to enlist the government of Ukraine in finding dirt on his putative presidential rival Joe Biden — and the extraordinary efforts by members of the administration to keep them from public view.The list of potential witnesses Democrats in the six House committees involved in the investigation may seek to interview keeps expanding, reflecting House Speaker Nancy Pelosi’s observation Friday on “Morning Joe,” updating Thursday’s accusation that Trump was engaged in a “cover-up” by saying the White House was now carrying out a “cover-up of the cover-up.”With the White House release of the summary of Trump’s call with Ukraine President Volodymyr Zelensky, the release of the whistleblower complaint and the testimony of acting Director of National Intelligence Joseph Maguire, numerous lines of inquiry have emerged. If Democrats were so inclined, they have enough potential witnesses to draw these proceedings out through the end of Trump’s term in office, which, while perhaps defeating the purpose of impeachment, could expose a much wider conspiracy in the U.S. government.Here is a rough, and likely incomplete, list of potential witnesses:Trump’s personal lawyer Rudy Giuliani The president’s personal lawyer was by his own admission — or boast — Trump’s point man in pressuring Ukrainian officials to investigate Biden and his son Hunter. While Giuliani has refused to say if he holds a security clearance, he has claimed that the State Department asked him to “go on a mission” to pursue a Ukrainian investigation of Biden.Attorney General William Barr In the summary of Trump’s call with Zelensky, the U.S. president mentions Barr five different times. “There’s a lot of talk about Biden’s son, that Biden stopped the prosecution and a lot of people want to find out about that, so whatever you can do with the attorney general would be great,” Trump said, according to the summary of his call. “I will tell Rudy and Attorney General Barr to call,” Trump says in another passage. The whistleblower also mentions Barr in his complaint, saying “Attorney General Barr appears to be involved as well.”Barr’s Justice Department advised the director of national security not to share the whistleblower complaint with Congress.Inspector General of the Intelligence Community Michael Atkinson After reading the whistleblower complaint against Trump, Atkinson deemed it “urgent” and sought to send it directly to congressional intelligence committees. Maguire, the acting director of national intelligence, intervened, sending it instead to the Department of Justice. Atkinson will testify before a closed session of the House Intelligence Committee on Oct. 4.President Trump, left, with U.S. Attorney General William Barr, Sept. 9, 2019. (Photo: Andrew Harnik/AP)Assistant Attorney General Steven Engel Engle wrote the opinion of the Justice Department that the whistleblower complaint “does not involve an ‘urgent concern,’” referring it instead to the criminal division of the Department of Justice rather than turning it over to Congress.FBI officials who received a referral regarding the whistleblower complaint On at least three occasions, the Justice Department contacted the FBI about the whistleblower complaint. Ultimately, however, the FBI deferred to the DOJ’s opinion that the call between Trump and Zelensky did not involve criminality.Former Director of National Intelligence Dan Coats Coats stepped down from his position on Aug. 15, nearly three weeks after the July 25 call between Trump and Zelensky. Yet Coats said this week that although the call was immediately flagged by White House staffers as problematic and the whistleblower’s complaint was filed on Aug. 12, he never saw it.Former DNI principal deputy Sue Gordon Trump refused to allow Coats’s deputy take over his position as DNI. She also resigned on Aug. 15.Former national security adviser John Bolton Before Bolton was fired by Trump on Sept. 9, he urged the president to not withhold $400 million in U.S. military aid to Ukraine to help the country protect itself against Russian aggression.Acting White House chief of staff Mick Mulvaney Trump directed Mulvaney to hold back the $400 million in assistance to Ukraine just one week before the president spoke on the phone with Zelensky. The administration has denied that Trump dangled a quid pro quo to Zelensky — restoring the funds in exchange for cooperation in probing Biden — but that possibility is likely to be a focus of the investigation.Office of Management and Budget acting Director Russell VoughtAfter ordering former Mulvaney to withhold the aid, Trump came under pressure to release the funds, which had been duly appropriated by Congress. He eventually gave Vought permission to release the money. Two House committees sent a letter to the White House Friday seeking all documents regarding the delay of military funds to Ukraine.Acting Director of National Intelligence Joseph Maguire (with back to camera) testifies on Sept. 26, 2019. (Photo: Andrew Caballero-Reynolds/AFP/Getty Images) Former U.S. Ambassador to Ukraine Marie Yovanovitch A career member of the foreign service, Yovanovitch was recalled to Washington in May in what the State Department described at the time as a “planned” departure. The whistleblower complaint, however, notes that there may have been a different motive. “Mr. Giuliani subsequently stated in an interview with a Ukrainian journalist published on 14 May that Ambassador Yovanovitch ‘was removed … because she was part of the efforts against the President,” the whistleblower wrote. She will be deposed on Oct. 2.White House counsel Pat Cipillone Cipillone helped oversee the unusual handling and storage of the summary of Trump’s call with Zelensky on a super-secure National Security Council server. House committees have asked his office for all White House records connected to the Ukraine issue, and have threatened a subpoena.National Security Council lawyers While their identity is not yet publicly known, attorneys at the National Security Council are reported to have carried out Cipollone’s instructions regarding the handling of the records of the president’s call. “NSC lawyers directed that the classified document be handled appropriately,” a senior White House official told CNN on Friday.Secretary of State Mike Pompeo Pompeo has defended officials in his department who were in contact with Giuliani about a Ukrainian investigation into Biden, but three House committee chairs have demanded documents detailing such communications. Appearing on Fox News, Giuliani has shown text messages he received from State Department officials.U.S. Special Representative for Ukraine Kurt Volker In a Fox News interview this week, Giuliani displayed a text message conversation he had with Volker in which the latter stated, “Mr. Mayor – really enjoyed breakfast this morning. As discussed, connecting you here with Andrey Yermak, who is very close to President Zelensky.” Volker will be deposed on Oct. 3, but on Friday he told Pompeo that he was resigning from the State Dept.State Department counselor T. Ulrich Brechbuhl Brechbuhl, who has close personal and business ties with Pompeo, listened in on Trump’s July 25 call with Zelensky. He is expected to be deposed on Oct. 8.U.S. Ambassador to the European Union Gordon Sondland The whistleblower complaint alleges that Sondland had a meeting with Ukrainian officials after Trump’s July 25 call and attempted to help “contain the damage” by Giuliani. Sondland is to be deposed on Oct. 10.Deputy Assistant Secretary of State George Kent In the wake of Trump’s call with Zelensky, Kent, a State Department official who will be deposed on Oct. 7, met with Ivan Bakanov, who heads Ukraine’s security service.