Two senior Senate Democrats, in a letter Tuesday to Defense Secretary Mark Esper, asked for details about the Pentagon’s role in freezing military aid to Ukraine for several weeks earlier this year.

The aid, which had been appropriated in law, is at the heart of the House impeachment inquiry amid allegations that President Donald Trump ordered the money withheld as a way to coerce Ukraine to help discredit Trump’s political rivals.

Sen. Richard J. Durbin of Illinois, the top Democrat on Appropriations, and Sen. Jack Reed of Rhode Island, the ranking member on Armed Services, asked Esper for a timeline of the aid freeze and a recounting of which officials were involved in the process, among other questions.

“The withholding of those funds raises serious concerns about the Department’s management of security assistance and the Administration’s compliance with its statutory obligations, potentially including the Impoundment Control Act of 1974,” Reed and Durbin wrote. “We are deeply concerned that the Administration decided to delay execution of this critical military aid to Ukraine and failed to inform the committees of this decision or provide a reason for the delay.”

On Sept. 25, Durbin, Reed and five other Senate Democrats had written Glenn Fine, the Pentagon inspector general, urging the IG to probe the Pentagon’s role in withholding the aid.

Meanwhile, the House Rules Committee chairman introduced a resolution Tuesday that lays out the format for the public phase of the House impeachment inquiry that will include witness hearings.

Here is the latest on the impeachment inquiry:

Testimony schedule: Kathryn Wheelbarger, acting assistant secretary of Defense for international security affairs, will not appear to testify as scheduled Wednesday. The committees are working to reschedule a date.

Catherine Croft, special adviser for Ukraine at the State Department, and Christopher Anderson, a language student at the State Department, are expected to appear in closed session on Wednesday, according to an official working on the impeachment inquiry.

Timothy Morrison, special assistant to the president and senior director for Europe and Russia on the NSC, is scheduled to give testimony on Thursday.

Robert Blair, assistant to the president and senior adviser to Mick Mulvaney, is expected to appear in closed session on Friday.

Constitutional showdown: Charles Kupperman, former deputy assistant to the president for national security affairs, did not appear for his deposition on Monday, setting up the latest showdown between the legislative and executive branches over fundamental constitutional powers.

An attorney for Kupperman had warned lawmakers that the former top deputy to ex-national security adviser John Bolton would not show up for his testimony unless a federal judge orders him to.

A status conference on the lawsuit is set for Thursday at 3 p.m., citing “the time-sensitive nature of the issues raised in this case.”

One-sided hearings: White House Press Secretary Stephanie Grisham reacted to House Democrats’ impeachment resolution by saying it merely would continue an “illegitimate sham.”

“It continues this scam by allowing Chairman Schiff, who repeatedly lies to the American people, to hold a new round of hearings, still without any due process for the President,” she said in a statement.

“The White House is barred from participating at all, until after Chairman Schiff conducts two rounds of one-sided hearings to generate a biased report for the Judiciary Committee,” Grisham said. “Even then, the White House’s rights remain undefined, unclear, and uncertain — because those rules still haven’t been written.”

Her statement focuses on process just a day after Trump urged House Republicans to recalibrate their defense of him from how House Democrats are conducting their probe to the substance of his July 25 call with Ukraine’s new president.

The resolution is in: House Rules Committee Chairman Jim McGovern on Tuesday introduced a resolution directing a handful of House committees to continue their investigations related to the House Democrats’ impeachment inquiry.

The resolution directs the House Intelligence, Oversight, Foreign Affairs, Ways and Means and Financial Services committees to continue investigating President Donald Trump. The House Rules Committee will mark up the resolution Wednesday in preparation for a Thursday vote.

House Republicans are whipping against the resolution setting procedures for the impeachment inquiry. Minority Whip Steve Scalise called the new information about the next stage of the probe a continuation of a “Soviet-style impeachment inquiry” in a note to GOP members.

A “sense of duty”: A National Security Council Ukraine expert who listened in on the July 25 telephone conversation between President Donald Trump and his Ukrainian counterpart is expected to tell impeachment investigators on Tuesday that he twice sounded the alarm to NSC lawyers regarding Trump’s interactions with Ukraine.

Army Lt. Col. Alexander S. Vindman plans to testify that he did so out of a “sense of duty” and that Trump’s attempts to coerce Ukrainian President Volodymyr Zelenskiy into investigating Trump’s domestic political rivals “would all undermine U.S. national security,” according to a rough draft of his opening statement, obtained by multiple media outlets.

Preemptive strike: Trump attempted Tuesday to discredit Vindman, relying an old tactic in an attempt to undermine the Army officer’s testimony.

Trump tweeted this (leaving off the necessary question mark and instead using a period): “Why are people that I never even heard of testifying about the call.” The commander in chief routinely tries to knock his political foes and those offering negative information about him down a peg in the public’s collective mind by contending he does not know them.

Trump’s implication, in this case, is Vindman is just a low-level NSC staffer who is offering weak testimony that offers a limited picture because he has no relationship to POTUS. But multiple public opinion polls suggest Trump’s tactics aren’t working, with clear majorities of Americans supporting impeachment.

Why are people that I never even heard of testifying about the call. Just READ THE CALL TRANSCRIPT AND THE IMPEACHMENT HOAX IS OVER! Ukrain said NO PRESSURE. https://t.co/VYmW8bYcgS

— Donald J. Trump (@realDonaldTrump) October 29, 2019

The president later declared  Vindman a “Never Trumper” and questioned whether he was on the same call, “ which Trump has repeatedly called a “perfect” one.

Supposedly, according to the Corrupt Media, the Ukraine call “concerned” today’s Never Trumper witness. Was he on the same call that I was? Can’t be possible! Please ask him to read the Transcript of the call. Witch Hunt!

— Donald J. Trump (@realDonaldTrump) October 29, 2019

“Shameful”: House Republican Conference Chairwoman Liz Cheney called attacks on Vindman’s patriotism “shameful.”

Former GOP Rep. Sean Duffy, now a CNN contributor, said Tuesday that Vindman has “an affinity for Ukraine,” and questioned his concern for U.S. interests.

House Minority Leader Kevin McCarthy said that he disagreed with Vindman’s assessment that Trump’s comments on the call with Zelenskiy could “undermine U.S. national security.”

“I thank him for his service and his commitment to this country. But he is wrong,” McCarthy said of Vindman.

Longer House session?: House Majority Leader Steny Hoyer pushed back when asked by a reporter Tuesday why Democrats weren’t canceling recess weeks to focus on the impeachment inquiry.

“Work is going to continue to be done by the committees, by those who are directly involved in the investigation and/or preparing for public hearings,” he said, specifically dismissing the notion the House could remain in session next week.

But when asked if there is a chance the House would be in past the first two weeks of December when their legislative year is scheduled to end, Hoyer conceded “There’s a chance.”

Essential info: The House Judiciary Committee on Tuesday officially opposed a Justice Department request to delay a district court judge’s order to turn over grand jury materials from the Mueller special counsel investigation into Russian interference in the 2016 election.

The committee argued that withholding disclosure “would cause severe harm to the Committee and the public by depriving the House of information essential to its ongoing impeachment investigation.”

Stand by your man: The president’s base appears to be sticking by his side, polling this week showed, despite mounting evidence that his administration sought Ukrainian assistance investigating his political foes in exchange for a military aid package.

While 81 percent of respondents to a Grinnell College poll released this week agreed that it is not OK for political candidates in the U.S. to ask for assistance from a foreign government to help them win an election — including 81 percent of self-identified Republicans — just 42 percent believe Trump should be impeached and removed from office, while 44 percent believe he should not.

“While nearly all Republicans believe that asking for foreign help to win an election is the wrong thing to do, in this case, most don’t believe it rises to the level of an impeachable offense,” said Grinnell College polling director Peter Hanson.

Forty percent of respondents to a USA TODAY/Suffolk University poll released Tuesday agreed with the president’s assessment that he is the victim of a political “lynching.”

Trash talk: Trump taunted House Democrats in another tweet, saying internal GOP polling suggests the impeachment probe will hurt Democrats come Election Day.

“Nervous Nancy Pelosi is doing everything possible to destroy the Republican Party. Our Polls show that it is going to be just the oppidite,” he wrote, misspelling opposite. “The Do Nothing Dems will lose many seats in 2020. They have a Death Wish, led by a corrupt politician, [House Intelligence Chairman] Adam Schiff!”

Nervous Nancy Pelosi is doing everything possible to destroy the Republican Party. Our Polls show that it is going to be just the oppidite. The Do Nothing Dems will lose many seats in 2020. They have a Death Wish, led by a corrupt politician, Adam Schiff!

— Donald J. Trump (@realDonaldTrump) October 29, 2019

The misspelling didn’t escape the attention of now-independent Rep. Justin Amash, who left the Republican Party because of Trump.

Your polls must have been done on Oppidite Day.

— Justin Amash (@justinamash) October 29, 2019

“Sense of duty”: Vindman, whose family fled then-Soviet-controlled Ukraine when he was 3 years old, reported Trump’s behavior with Ukraine to NSC lawyers “out of a sense of duty,” he planned to tell House impeachment investigators.

Vindman was listening in on the July call between Trump and Zelenskiy on which Trump appeared to ask his Ukrainian counterpart to launch an anti-corruption investigation into former Vice President Joe Biden, his son Hunter Biden, and Burisma, a Ukrainian gas company on whose board Hunter Biden sat. Joe Biden is widely considered the current frontrunner to be the Democratic presidential nominee in 2020.

“I did not think it was proper to demand that a foreign government investigate a U.S. citizen, and I was worried about the implications for the U.S. government’s support of Ukraine,” Vindman planned to say in his opening statement. “I realized that if Ukraine pursued an investigation into the Bidens and Burisma it would likely be interpreted as a partisan play which would undoubtedly result in Ukraine losing the bipartisan support it has thus far maintained.”

Vindman was also expected to challenge statements made to House investigators by Trump-appointed U.S. Ambassador to the European Union Gordon Sondland, who largely defended the president against allegations of wrongdoing during his testimony earlier this month. Sondland told lawmakers on Oct. 17 that he recalled “no discussions” mentioning the Bidens or Burisma.

Vindman will be at least the second administration official to contradict Sondland, who, according to Vindman, repeatedly stressed the importance of having Ukraine investigate the Bidens at a meeting with Ukrainian officials on July 10 and at a subsequent debriefing.

“I stated to Amb. Sondland that his statements were inappropriate, that the request to investigate Biden and his son had nothing to do with national security, and that such investigations were not something the NSC was going to get involved in or push,” Vindman said in his opening statement. Sondland was told by multiple other officials that his comments about the investigations were inappropriate, Vindman was expected to say.

From refugee to NSC: The draft of Vindman’s opening statement succinctly outlines his extraordinary background as a refugee who escaped Ukraine, was raised in New York City in the 1980s, earned an Ivy League degree, served in the U.S. Army for more than two decades, and eventually became a Ukrainian expert on Trump’s national security council.

Vindman has served multiple tours in South Korea, Germany, and Iraq, where he was awarded a Purple Heart after being wounded in an IED attack.

“I have dedicated my entire professional life to the United States of America,” Vindman planned to tell lawmakers.

In writing: House Rules Chairman Jim McGovern is expected to introduce a resolution today that would affirm the authority of the impeachment inquiry and establish procedures for the public phase of the investigation.

Speaker Nancy Pelosi announced Monday that the House will vote Thursday on the resolution.

House Republican leaders will urge their members to vote against the resolution, Minority Whip Steve Scalise told CQ Roll Call Monday night.

“It legitimizes a tainted process that’s rooted in Soviet style justice, and I think Pelosi admitted defeat by the fact she’s bringing it to the floor,” the Louisiana Republican said.

Senate Judiciary Chairman Lindsey Graham claimed victory that House Democrats would vote on the impeachment process.

“There is no doubt in my mind that the overwhelming response House Democrats heard from the American people and Senate Republicans in support of my resolution forced their hand. Today’s announcement is an acknowledgment of the success of our efforts last week,” Graham said.

[Democrats control narrative in impeachment inquiry]

Pelosi disputed that: “This is a resolution on how we proceed in the committees. Understand, it is not a resolution of any inquiry. That is already done.”

“Firsthand” information: Intelligence Chairman Adam Schiff said the resolution the House will vote on will establish the format for open hearings that will be conducted by his committee.

“The American people will hear firsthand about the President’s misconduct,” he said.

It was unclear from Schiff’s statement whether the Oversight and Foreign Affairs committees, which have been working with the Intelligence panel to conduct closed-door witnesses depositions, will be able to participate or host their own public hearings.