Impeachment inquiry: What to watch in the week ahead

The pace of House Democrats' investigation into President Trump and Ukraine will accelerate this week with a series of hearings from key administration officials, including a highly anticipated appearance from a top official on the National Security Council.

What we're watching: Tim Morrison, the NSC's Russia and Europe director, will be the first currently serving White House official to testify before the committees on Thursday. He's also the first official who is believed to have been on the July 25 call between Trump and Ukrainian President Volodymyr Zelensky, which is at the crux of the Dems' inquiry.

• Democrats are eager to ask Morrison about the explosive testimony of Bill Taylor, the top U.S. diplomat in Ukraine. Taylor said Morrison had been told that Trump insisted Zelensky publicly commit to investigating the 2016 election and the Bidens, and that hundreds of millions of dollars in aid to Ukraine hinged on his willingness to do so.
• Worth noting: Morrison's name appeared 15 times in Taylor's opening statement.

Meanwhile, the White House is being stymied in its efforts to prevent current and former officials from complying with the committees' requests, and Morrison appears to be no exception.

• Morrison's lawyer told Politico that "If subpoenaed, Mr. Morrison plans to appear for his deposition.”

Trump, who compared the impeachment inquiry to a "lynching" this week, has been extremely frustrated with Democrats' investigation, and he has lashed out at the officials cooperating.

• The president has specifically singled out Taylor — who was handpicked by Secretary of State Mike Pompeo — calling him a "Never Trumper" and adding that "Never Trumpers" are "human scum."

But three veterans who have served with Taylor defended him in powerful interviews with CNN's Jake Tapper and Kate Sullivan, describing him as a "man of honor," "public servant" and "role model" who "represents the best of our Department of State."

What's next: The following current and former administration officials are also scheduled to testify this week:

• Tuesday, Oct. 29 at 9:30 am: National Security Council Director for European Affairs Lt. Col. Alexander Vindman.
• Wednesday, Oct. 30 at 9:30 am: Acting Assistant Secretary of Defense for International Security Affairs Kathryn Wheelbarger.

Former Deputy National Security Adviser Charles Kupperman was subpoenaed by the House committees to appear on Monday.

• However, Kupperman filed a lawsuit on Friday asking a federal judge to rule on whether he can testify, given that Trump has asserted that he is immune from the congressional process and instructed him not to testify.