Justice Dept. Threatens House Democrats Over Contempt in Barr Battle

From a more practical view, the letter from Mr. Boyd bolstered the record that the executive branch could point to in order to make the case that Congress was unreasonable if, as seems likely, the dispute ends up in a lengthy court battle over whether Congress’s subpoena, or Mr. Trump’s for-now still hypothetical assertion of executive privilege, should prevail.

Complying with the subpoena, wrote Mr. Boyd, “would force the department to risk violating court orders and rules in multiple ongoing prosecutions,” as well as require it to violate grand jury secrecy rules.

The showdown between the House and White House over Congress’s constitutional role in oversight of the executive branch is also profoundly dividing the Capitol, where House Democratic leaders are getting no backup from their Senate Republican counterparts. Senator Mitch McConnell of Kentucky, the majority leader, stood on the floor of the upper chamber on Tuesday and pressed an entirely different verdict: “Case closed.”

In a blistering speech, Mr. McConnell targeted President Barack Obama for his policy toward Russia (“maybe stronger leadership would have left the Kremlin less emboldened”) and Democrats in Congress for refusing to accept Mr. Mueller’s conclusions.

“With an exhaustive investigation complete, would the country finally unify to confront the real challenges before us?” Mr. McConnell asked. “Or would we remain consumed by unhinged partisanship, and keep dividing ourselves to the point that Putin and his agents need only stand on the sidelines and watch as their job is done for them?”

“Regrettably,” he continued, “the answer is obvious.”

Senator Chuck Schumer of New York, the Democratic leader, and Speaker Nancy Pelosi, in a joint statement, blasted the speech as a “stunning act of political cynicism and a brazen violation of the oath we all take.”

Beyond the messaging, the divergence could shape what Democrats are able to do to further hold Mr. Trump to account for Mr. Mueller’s findings on Russian election interference and attempts by the president to thwart his investigation. Mr. McConnell’s uncompromising stand signaled that a House impeachment resolution would face a stone wall in the Senate, where Mr. Trump would be put on trial.