WASHINGTON — Almost from the moment that Speaker Nancy Pelosi and her lieutenants decided this fall to pursue the impeachment of President Trump, they made a fateful judgment: If the president intended to do nothing but stonewall and subvert their inquiry, they were not going to be the ones politely sticking to lofty traditions.

Mr. Trump’s lawyers have made a similarly cold calculation. After a year of defying without consequence Congress’s attempts to investigate the president’s conduct, they have no intention of taking part in what they view as an illegitimate impeachment, initially conducted without a formal House vote in a break with recent precedent.

The clash comes to a head on Monday with a hearing in the Judiciary Committee where Democratic lawyers plan to present the case for impeaching Mr. Trump while the White House sits out the process. That will set in motion a rapid-fire set of actions likely to produce official charges against the president by week’s end and a nearly party-line vote in the full House before Christmas to impeach him.