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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.

What's next in the inquiry: 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.