Now, as Senate Republicans refuse to take up the bills they pass, Trump administration witnesses refuse to show up for their hearings and the president levels his own highly unusual lawsuits against the House’s oversight requests, two of the three branches of government are regularly facing off before the third, creating a new stress with uncertain consequences for the political system.

“It is unprecedented,” said Charles Tiefer, a former longtime House lawyer who is now a University of Baltimore law professor. “The challenges for the House counsel ebb and flow over time, but this is like nothing else in history.”

The consequences of the specific disputes could be significant. In the short term, they could determine whether House Democrats are able to drag information to light about Mr. Trump that could lead to his impeachment or damage his re-election prospects. And potential decisions by the higher courts could clarify the long-ambiguous line between a president’s secrecy power and Congress’s oversight authority — determining whether future presidents can systematically stonewall congressional subpoenas.

But the broader phenomenon is also significant.

As an immediate matter, the surge in litigation is a consequence of Mr. Trump’s norm-busting presidency. House Democrats are looking for additional venues through which to take him on — or, in some cases, fighting lawsuits that the president filed against Congress himself to try to block lawmakers from obtaining information about him from entities outside the federal government. But it is also bringing into clearer view how, over the past generation, Congress was already starting to go to court more often than had been the historical norm, as political compromise gave way to deadlock amid growing partisan polarization.

That trend line suggests that even if the number of congressional lawsuits declines when the next president takes office, the constitutional order could change in a way that Mr. Tiefer a nd other legal scholars view as dangerous. He said it is better if the two parties were able to resolve high-level policy disputes through compromise rather than through the “rigid and formalized system” of litigation, and suggested that routinely pushing those disputes into court could heighten politicization of the judiciary.