WASHINGTON – The U.S. diplomat who called President Donald Trump’s demand for Ukraine to investigate a political rival in exchange for military aid “crazy” takes center stage Tuesday, as the House impeachment inquiry enters its fifth week.

Other witnesses scheduled for closed-door depositions with the three committees – Foreign Affairs, Intelligence, and Oversight and Reform – include budget and defense officials. Democrats leading the inquiry have said they want to learn more about how Trump withheld nearly $400 million in military aid while asking Ukraine President Volodymyr Zelensky in a July 25 call to investigate former Vice President Joe Biden and his son Hunter.

House Republicans expect to vote Monday on a resolution censuring the leader of the inquiry, Intelligence Committee Chairman Adam Schiff, D-Calif. A Republican leader also proposed to change House rules so that any lawmaker could attend the sessions. Republicans have complained about limited access to the sessions.

Monday: GOP calls for Schiff censure

House Minority Leader Kevin McCarthy, R-Calif., said Friday there would be a vote Monday on a resolution to censure Schiff. The resolution is unlikely to be approved because Democrats hold a majority in the 435-member chamber, but it is co-sponsored by 165 Republicans.

McCarthy said Schiff has lied repeatedly during the investigation of Trump. McCarthy argued that Schiff should be held to a higher standard as chairman of the Intelligence Committee because he is privy to information that rank-and-file members don’t receive.

“He has tried to hide so many of the facts, and then when he was put in position to give the facts, he lied about them,” McCarthy said. “He should be held accountable just like every other member.”

Despite GOP complaints, House Speaker Nancy Pelosi, D-Calif., has repeatedly supported Schiff's leadership in the inquiry.

"I'm very proud of the work that Adam Schiff is doing," Pelosi told reporters Thursday. "And this isn't about politics or partisanship. It's about patriotism for our country, and I value the way he is conducting this with equal time on all sides for the questioning that are there."

The censure vote comes after Republicans who aren't on the three key committees tried repeatedly last week to attend the closed-door sessions. But lawmakers were blocked at the door, under a ruling from Schiff and the House parliamentarian.

The second-ranking Republican in the House, Rep. Steve Scalise, R-La., introduced a resolution Friday with Rep. Tom Cole, R-Okla., to allow all lawmakers to attend all impeachment proceedings including closed-door depositions and transcribed interviews.

“The American people's elected representatives have been denied access to relevant documents and the opportunity to attend depositions and transcribed interviews,” Scalise said in a statement. “Chairman Schiff wants to impeach President Trump behind closed doors and clearly has no intention of conducting a fair and open process.”

Schiff has said the closed sessions are necessary to prevent witnesses from hearing each other's testimony, as happens in a criminal investigation. But Schiff said he anticipates transcripts of the closed sessions will be released and public hearings will be held.

Schiff also said Republicans on the committees and their staffers have been given unlimited time to ask questions of the witnesses. The parties typically alternate an hour or 45 minutes at a time for each side, during sessions that have lasted as long as 10 hours.

"All of the members of these three committees have been invited to attend and participate and ask questions," Schiff said Tuesday. "They have been very professionally done."

Tuesday: ‘Crazy’ Ukraine policy

William Taylor, the top U.S. diplomat in Ukraine, questioned Trump’s Ukraine policy in texts revealed as part of the inquiry. Taylor is scheduled to testify privately Tuesday before the House inquiry.

On Sept. 1, Taylor asked Kurt Volker, the U.S. special envoy to Ukraine, and Gordon Sondland, the U.S. ambassador to the European Union, whether security assistance and a White House meeting between Trump and Zelensky depended upon an investigation.

Sondland told Taylor to call him. But Sept. 9, Taylor repeated his concern in another text.

"As I said on the phone, I think it's crazy to withhold security assistance for help with a political campaign,” Taylor said.

Sondland later said that he called Trump before responding that the assertion was “incorrect.”

“The President has been crystal clear no quid pro quo’s of any kind,” Sondland said in a text message, which he said relied on the president’s assurance.

Sondland testified Thursday that he was disappointed that Trump delegated Ukraine policy to his private lawyer, Rudy Giuliani. Sondland also said he wasn’t aware that Trump asked Zelensky to investigate Biden or that military aid was withheld.

But acting White House chief of staff Mick Mulvaney said Thursday that military aid was withheld for a Ukraine investigation of interference in the 2016 election. Trump urged Zelensky to investigate the Bidens during a July 25 call.

Trump has insisted he was absolutely justified in asking Ukraine to fight corruption.

Wednesday: Military aid

House investigators want to learn more about how military aid was withheld from Ukraine. But the Defense Department and the White House Office of Management and Budget (OMB) have defied House subpoenas for documents about the funding.

Pat Cipollone, the White House counsel, notified the House on Oct. 8 that the administration wouldn’t cooperate with the investigation because the House hadn’t voted to authorize it. But House Speaker Nancy Pelosi, D-Calif., said no vote is needed after she declared a formal impeachment inquiry Sept. 24. Schiff has warned that the House could consider defying subpoenas could be considered obstruction of justice in any articles of impeachment.

Despite the administration’s defiance, several officials such as Sondland have testified. The House inquiry scheduled a closed-door meeting Wednesday with Laura Cooper, a deputy assistant secretary of Defense.

Scheduling for the week was rearranged for memorial services Thursday and Friday for the late Rep. Elijah Cummings, D-Md., who was chairman of the Oversight committee. Cooper's session had been set for Thursday and was moved up a day, while others have been postponed.

The inquiry had planned to meet Wednesday with Philip Reeker, the acting assistant secretary of State for the European and Eurasian Affairs, and Michael Duffey, the associate director for national security programs at OMB.

But Russ Vought, the acting director of OMB, tweeted Monday that Duffey wouldn't be cooperating with the inquiry, as explained by the White House letter.

Reeker's appearance was rescheduled for Saturday.