“It has been our practice to not disclose testimony, but to reveal when witnesses refuse to answer questions,” Schiff said. “We don’t allow witnesses to say publicly that they’re cooperating, when they have actually refused to answer our questions.”

In an interview last December, Trump Jr. declined to answer the committee’s questions about a phone conversation he had with his father in July 2017 about the June 2016 Trump Tower meeting. An attorney had been present on that call, too, Trump Jr. said, so he was shielded by attorney-client privilege.

Democrats were incredulous—that’s not how attorney-client privilege works, they argued.

“So we called him out on that,” Schiff said. “And obviously that was threatening to the White House. They’ve been attacking me ever since.”

There was another, more immediate trigger for Trump’s early-morning tweet, Schiff said: the House Intelligence Committee’s impending vote on whether to release the Democrats’ 10-page response to chairman Devin Nunes’s accusations of surveillance abuses carried out by the Justice Department.

The committee voted to release the rebuttal on Monday and sent it to the White House to review and ultimately declassify.

“The president is unhappy about being in the position of having to declassify our rebuttal to the Nunes memo, which he thinks is vindication for him, because it will reveal how flawed the Nunes memo is,” Schiff told me. A spokesperson for Nunes did not immediately reply to requests for comment.

A GOP aide who requested anonymity to speak freely about the investigation said he doesn’t think Trump “has ever faced an adversary quite like Schiff, and it’s freaking him out.”

“First off, he’s a skilled prosecutor with an acid tongue, and a command of all the facts including the most deeply held classified information,” the aide told me. “Second, he’s not in leadership and therefore doesn’t have to consider being at the negotiating table like [Chuck] Schumer or [Nancy] Pelosi do. Third, he’s got a squeaky clean record (wouldn’t have ascended to that position if he didn’t) and comes from a district where when Trump lashes out at him, it only makes him more powerful and popular.”

Speculation swirled on Monday night about whether Trump would actually declassify a document written primarily by Schiff and his staff that could undermine Nunes, whom the president called a national hero in a separate tweet on Monday. The White House has said that it will consult with the FBI and DOJ about any recommended redactions to the rebuttal memo’s content—a process Schiff said the Democrats will hopefully be able to monitor.

“We’ve asked the DOJ and FBI to report to us any redactions they’re recommending to the White House so we can separate legitimate redactions, if any, from any political ones,” Schiff said. “So hopefully we’ll have visibility into that.”