“They’re getting what they want,” Khanna said on CNN on Monday, referring to congressional Republicans. “Let’s see now what excuse they have.”

The move has already led to a pause among Senate Republicans considering a resolution to condemn the House's impeachment process, who are divided over whether to continue pressing the proposal. The resolution was referred to the House Rules Committee and Chairman Sen. Roy Blunt (R-Mo.) said he would need to see how Pelosi handled the inquiry this week before moving forward.

Shortly after the vote on the resolution was announced Monday, several senior Democratic aides were struggling to explain the rationale, having been given little notice of it themselves and expressing concern about the long-term political impact it could have on the caucus’ most vulnerable members.

Some moderate Democrats are already anxious about the plan, after making clear to leadership that they wanted to avoid any unnecessary floor votes on impeachment.

Democrats have spent weeks fighting GOP attempts to cast doubt on the legitimacy of their impeachment inquiry, which has spanned dozens of interview requests and subpoenas for documents and testimony.

White House and GOP leaders are already calling the resolution proof that Democrats’ inquiry was not valid without a vote.

“Speaker Pelosi is finally admitting what the rest of America already knew — that Democrats were conducting an unauthorized impeachment proceeding," White House spokeswoman Stephanie Grisham said in a statement, slamming Democrats for "secret, shady, closed door depositions."

“Today’s backtracking is an admission that this process has been botched from the start,” added House Minority Leader Kevin McCarthy (R-Calif.) wrote on Twitter.

House Intelligence Committee Chairman Adam Schiff (D-Calif.) was pushing for the resolution, according to multiple Democratic sources. Schiff said Monday that open hearings will be conducted by the House Intelligence Committee.

Top Democrats, recalling the Judiciary Committee’s messy September hearing with former Trump campaign manager Corey Lewandowski, are hopeful to implement detailed changes to the process to prevent future witnesses from disrupting proceedings.

One of the more significant changes, described by three Democratic sources, would allow lawmakers and staff to question witnesses for longer than House rules typically allow. Under existing House rules, lawmakers typically get five minutes apiece to question witnesses, with Republican and Democratic members alternating. The resolution would permit each side a longer, uninterrupted round of questioning that can be divided up among lawmakers and staff — similar to the way witnesses have been questioned in closed-door depositions.

Under current House rules, committees already have the option to grant the chairman and ranking Republican an additional 30 minutes of uninterrupted time, and a second option to give committee staff of each party 30 minutes apiece.

One option being discussed is providing more time for legal counsel on the committee to question witnesses once the House begins to have open hearings.

Many Democrats have said the only bright spot of the Lewandowski hearing was when a Democratic lawyer for the Judiciary Committee, Barry Berke, forced Lewandowski to admit episodes of dishonesty. Changing the rules could establish clear guidelines for conducting these sessions in public.

Democrats have always hoped to wrap up their investigation by the end of the year — with many believing it will culminate in a full House vote on articles of impeachment. The resolution will mark the first floor vote on impeachment since Democrats formally launched their inquiry a month ago.

The vote could cause heartburn across the caucus, after Democrats spent weeks shooting down GOP attacks on their impeachment process. Many Democrats believed they had won the argument after Friday’s ruling that validated the Democrats’ strategy and made clear that no vote was needed. Judge Beryl Howell, who wrote the extensive ruling, slammed Republican arguments as “at worst, red herrings and, at best, incorrect.”

Pelosi herself said in Monday’s letter that the GOP’s argument that the impeachment inquiry was invalid “has no merit.”

“They argue that, because the House has not taken a vote, they may simply pretend the impeachment inquiry does not exist,” Pelosi wrote.

But Democrats now appear to be taking the precise vote that Republicans wanted: Voting to formalize the ongoing investigation.

Over the last month, House Democrats have struggled with the public-facing aspect of their impeachment probe, with their caucus’s own investigators wrapped up in a half-dozen secret depositions. The interviews have yielded key details, though specifics can’t be made public until the panels have talked to several other witnesses, Democrats say.

But pressure is also mounting for public hearings, with Republicans taking high-profile steps — like last week’s stunt in which dozens of House Republicans barged into a closed-door deposition — to underscore the closed-door nature of the inquiry so far.

POLITICO NEWSLETTERS POLITICO Playbook Sign up today to receive the #1-rated newsletter in politics. Sign Up Loading By signing up you agree to receive email newsletters or alerts from POLITICO. You can unsubscribe at any time. This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

In response, Schiff and other top Democrats are planning ways to speed up the process to more quickly get to the public phase of their investigation, including holding weekend sessions and bringing in multiple witnesses per day.

But Democrats are also wrestling with another question — what to do if administration officials refuse to cooperate in the probe.

Charles Kupperman, a former senior national security official, defied a subpoena ordering him to appear before House investigators on Monday. On Friday Kupperman, who served as deputy to former national security adviser John Bolton, asked the courts to decide whether he’s required to testify after Trump directed him to defy the subpoena.

Bolton, who is represented by the same lawyer, is expected to follow the same judicial directive given to Kupperman when summoned by House investigators.

House Rules Committee Chairman Jim McGovern (D-Mass.) plans to unveil text of the resolution by Tuesday afternoon.

“As committees continue to gather evidence and prepare to present their findings, I will be introducing a resolution to ensure transparency and provide a clear path forward, which the Rules Committee will mark up this week,” McGovern said in a statement. “This is the right thing to do for the institution and the American people.”

Andrew Desiderio, Burgess Everett and John Bresnahan contributed to this report.