In an interview on NBC News' "Meet The Press", Nadler said articles of impeachment would likely be drawn up by his committee by the end of the week. "But the fact is we're not going to make any decision as to how broad the articles should be - as to what they contain, what the wording is - until after the hearing tomorrow". Asked on CNN if lawmakers could vote this week, he said, "It's possible".
"The evidence shows that Donald J. Trump, the president of the United States, has put himself before his country. He has broken his oath", Nadler said.
Democrats need to settle the question of whether to draft a third article alleging obstruction of justice based on former Special Counsel Mueller's report on Russian interference in the 2016 presidential election.
Still, House Intelligence Chairman Adam Schiff, a California Democrat, seemed to indicate he did not support including the Mueller allegations in the impeachment articles. "We need to be focused; we need to be clear".More news: Hong Kong protests mark six-month anniversary
House Judiciary Committee counsel Barry Berke is expected to detail a pattern of Trump's behavior in his opening statement, which will likely include some discussion of the details of the Mueller report, the sources said.
Scheduled to testify on Monday was a bipartisan group of lawyers from two House committees: the intelligence committee, which investigated Trump's efforts to pressure Ukraine to investigate Joe Biden; and the judiciary committee itself, which investigated Mueller's findings.
Last week, three legal professors argued that Trump's conduct in his dealings with Ukraine was evidence of impeachable offenses.
"It's part of a pattern" that poses a threat to the integrity of the November 2020 election, Nadler said.More news: Saudi Arabia ends gender-segregated entrances for restaurants
Republicans are demanding that Nadler postpone Monday's hearing to give them time to review the material.
Ukraine will be the dominant focus Monday, as House Intelligence Committee counsel Dan Goldman will lay out the committee's investigation and will be the one answering questions during the bulk of the hearing.
Republican Matt Gaetz, a Trump supporter on the Judiciary Committee, told ABC the president's impeachment was "inevitable" as Republicans began to emphasize the vote margin as the thing to watch.
The issue would then move to the full House of Representatives where its Democratic majority would be widely expected to approve them, as early as the Christmas recess, sending the impeachment process to the Republican-led Senate for a trial in January.More news: National Basketball Association career-high for Simmons in Sixers rout