The White House is preparing for another showdown against House Democrats, this time over testimony from former White House counsel Don McGahn. The Washington Post reports that the White House is reportedly planning to use executive privilege to block McGahn from complying with a congressional subpoena, after McGahn’s comments to special counsel Robert Mueller pointed toward potential instances of the president obstructing justice. Democrats, however, aren’t prepared to let their subpoena fail without a fight, escalating an already-combative relationship as the House attempts to investigate President Donald Trump in the wake of the Mueller report.

Per the Post, the move to block McGahn’s testimony is part of a broader effort to thwart House Democrats from securing testimony from current and former White House aides, and comes after White House deputy counsel Michael M. Purpura instructed former personnel security director Carl Kline not to appear before Congress. In a separate interview with the Post on Tuesday, Trump said that while he has not “made a final, final decision” over whether to invoke executive privilege, complying with congressional requests is apparently “unnecessary.” “There is no reason to go any further, and especially in Congress where it’s very partisan—obviously very partisan,” Trump claimed. “I allowed my lawyers and all the people to go and testify to Mueller. . . . I was so transparent; they testified for so many hours. They have all of that information that’s been given.”

Democrats, for their part, are fighting back. House Oversight Chair Elijah Cummings said he intends to consider whether to hold Kline in contempt for violating his subpoena, and the House Judiciary chair, Rep. Jerrold Nadler, issued a statement Tuesday night in response to the White House’s reported McGahn move. “The moment for the White House to assert some privilege to prevent this testimony from being heard has long since passed,” Nadler wrote. “I suspect that President Trump and his attorneys know this to be true as a matter of law — and that this evening’s reports, if accurate, represent one more act of obstruction by an Administration desperate to prevent the public from talking about the President’s behavior.” House leadership has been bullish on investigating Trump and his potential obstruction post-Mueller—even as they’ve remained skittish on the topic of impeachment—with House Speaker Nancy Pelosi saying in a conference call with the caucus, “We have to save our democracy.”

The Trump administration has been forcefully resisting House Democratic probes: according to a statement from Cummings, “the White House has refused to produce a single piece of paper or a single witness in any of the Committee’s investigations this entire year.” And the administration has only ramped up their efforts post-Mueller. Treasury Secretary Steven Mnuchin missed yet another deadline Tuesday to hand over Trump’s tax returns as the House had requested, while the Trump administration filed a lawsuit against Cummings after the Oversight Committee subpoenaed accounting firm Mazars USA for Trump’s financial documents. “This is as close to anarchy as I have seen,” Charles Tiefer, former solicitor and deputy general counsel of the House, told Politico. “The administration seems to think it has floated off into space and no longer subject to oversight.”

The White House’s belief that it’s not subject to oversight and the legal realities, of course, are two different things. With both the House and White House seemingly at a stalemate, the Trump-House showdown will likely ultimately be left in the hands of the judicial branch—including, potentially, the U.S. Supreme Court. Trump’s success there, though, remains a long shot. The legal basis for Trump’s lawsuit against Cummings cites an 1880 Supreme Court decision that was later overturned, and Tiefer described the suit to the Post as “an act of desperation by the Trump lawyers.” Trump’s new plan to use executive privilege is expected to also face legal challenges, experts cited by the Post noted, though in the meantime it will likely help to stall Democrats’ efforts to take the Mueller probe into their own hands. “It seems to me executive privilege was waived when McGahn was permitted to give testimony and to be interviewed by special counsel Mueller,” former Watergate prosecutor Richard Ben-Veniste told the Post. “I don’t see how the White House can assert executive privilege with something that has already been revealed. To use the Watergate expression, ‘You can’t put the toothpaste back in the tube.’”

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