(CNN) House Democrats say they are undeterred by the White House preventing first-hand witnesses from testifying before the House Intelligence Committee — and now are actively preparing for the next step in their eight-week-old investigation and the likely impeachment of President Donald Trump.

Privately, Democrats are anticipating a busy December that will be filed with proceedings before the House Judiciary Committee, including public hearings and a markup, and a likely vote to impeach Trump on the House floor by Christmas Day, according to multiple Democratic sources, which would make him just the third President in history to be impeached.

The House Intelligence Committee, along with two other panels, are writing a report detailing their findings, which is expected to serve as the basis for articles of impeachment that the House Judiciary Committee will consider.

Democrats say they are still debating the size and scope of the articles, which are likely to focus on abuse of power, obstruction of justice, obstruction of Congress and bribery.

But despite speaking with 17 witnesses behind closed doors, including 12 witnesses in just a week of public testimony, Democrats have not obtained crucial documents or spoken with several key officials because the White House and State Department have refused to comply with subpoenas.

That has left top Democrats with a choice: They could fight in court to obtain potential smoking-gun documents and testimony from acting White House chief of staff Mick Mulvaney, Secretary of State Mike Pompeo and former national security adviser John Bolton. Or Democrats could move forward with the evidence they have.

House Speaker Nancy Pelosi has chosen the latter.

In some of her most direct comments to date, Pelosi said Thursday they wouldn't delay their impeachment push to fight for those witnesses through court battles, saying instead that would be up for the Senate to decide in a potential trial about whether the President should be removed from office.

"They keep taking it to court and no, we're not going to wait until the courts decide," she said. "That might be information that's available to the Senate in terms of how far we go and when we go, but we can't wait for that because again it's a technique. It's obstruction of justice, obstruction of Congress, so we cannot let their further obstruction of Congress be an impediment to our honoring our oath of office."

Pelosi added: "We cannot be at the mercy of the courts."

Pelosi at this point does not look like she can count on any Republican votes to impeach Trump. House Minority Leader Kevin McCarthy told CNN that he was not going to lose any members.

"I think we are going to gain Dems," McCarthy, a California Republican, said Thursday.

Rep. Eric Swalwell, a Democrat who sits on House Intelligence and Judiciary committees, said "it's more relevant" that any information the key witnesses may be able to share.

Speaker of the House Nancy Pelosi holds a press conference with House Intelligence Chairman Adam Schiff in Washington, DC, on October 15.

"We're not going to chase any of these obstructers into the courts anymore; we have a solid case. We have evidence of abuse of power, of extortion, bribery, obstruction of Congress," Swalwell said. "And we're going to consider all of that evidence as we make a determination on what should be sent if anything to the Judiciary Committee."

But as soon as Monday, the court could throw a wrinkle in the process with a ruling expected over whether former White House counsel Don McGahn should testify before the Judiciary Committee over the allegations of obstruction of justice detailed in the Mueller report.

If Democrats win that case, there could be more pressure to force those other key witnesses to testify. And such a ruling would intensify debate among Democrats to wrap into articles of impeachment the 10 allegations that Trump obstructed justice derailed in the Mueller report, as well as whether he lied to the special counsel. Pelosi has favored to keep the focus on Ukraine , arguing it's a clear case of bribery that undercut national security.

Yet some Democrats think that it makes sense to make a more forceful push to secure the testimony of the first-hand witnesses, including Bolton, whose attorney warned he would fight a subpoena in court, as well as Trump's personal attorney Rudy Giuliani, Mulvaney and Pompeo. And the wait is worth it, they say, given the gravity of impeaching the President.

US President Donald Trump speaks as National security advisor John Bolton listens during a meeting in May 2018 in Washington DC. Democrats want to hear from Bolton in their impeachment inquiry but he has thus far refused to show.

Several Democrats told CNN that those witnesses could remove any doubt that Trump employed the power of the US government -- by withholding roughly $400 million in military aid and a White House meeting sought by Ukrainian President Volodymyr Zelensky -- in order to get Ukraine to announce investigations that could help Trump politically.

"Look I would love to have these witnesses in," said Rep. Jim Himes, a Democrat on the House Intelligence Committee. "It is clear that the secretary of state knew about the firing and complied with the firing of this ambassador who had 33 years of excellent service. I want to ask him about that, I want to ask him who pressured him to do that and how he could see his way to firing somebody who had superb recommendations who had done an extraordinary job.

"And of course we need to learn more about exactly what Rudy Giuliani was saying to people in Ukraine," Himes added.

Rep. Dean Phillips, a Minnesota Democrat who participated in the closed-door depositions, told CNN that with the volume of testimony, the committees could slow down to just allow the information to breathe.

Yet many others say that the fast-paced investigation has turned over a mountain of evidence to show Trump pressured Ukraine to probe former Vice President Joe Biden and his son Hunter -- along with an unsubstantiated theory that Ukraine interfered with the 2016 US elections to help Democrats. Any evidence that the White House has not turned over, Democrats say, will be used as evidence that Trump sought to obstruct Congress.

"I think we have been hampered in our ability because the White House, the State Department, the Department of Defense have all withheld documents from us," said Rep. Jackie Speier, a California Democrat and member of the House Intelligence Committee. "But even with our hands tied behind our backs, we've been able to present the American people a compelling argument for moving forward with a review of whether or not we should have articles of impeachment bought to the floor of the House."