Democrats believe the Republicans abused the power of the majority to hobble the Obama administration, deeply damage Hillary Clinton and protect Mr. Trump. That frustration, coupled with what most lawmakers expect to be a wave of Democratic anti-Trump outrage fueling midterm victories, could overwhelm the instincts of more moderate members of the party to chart a different, more bipartisan course than Republicans have.

Democrats on the Oversight Committee, typically the House’s most muscular investigative body, have more than 50 subpoena requests that have been denied by committee Republicans since Mr. Trump took office, from the administration of security clearances at the White House to chartered jet travel by cabinet officials to Justice Department documents related to its decision not to defend the Affordable Care Act in court.

“It’s not like we have to go dig them up. They are right there sitting on the desk,” Mr. Cummings said.