As if tensions and expectations weren’t already high enough surrounding Robert Mueller’s testimony today, along comes a twist right out of an episode of Law & Order. The special counsel has added a witness in one of today’s hearings and an advisory counsel in the other, and … they’re both the same man. Aaron Zebley, who served as Mueller’s deputy, will help Mueller answer questions from the House Judiciary Committee and then will testify himself at a House Intelligence Committee later:

Democrats on the House Judiciary Committee agreed to allow Aaron Zebley, a former top deputy to Mueller, to sit beside him and advise him in his answers. The accommodation came after Mueller asked that Zebley be allowed to testify as a witness next to him, a request Judiciary Democrats rejected. The House Intelligence Committee, meanwhile, has agreed to let Zebley be sworn in for its hearing later in the day, according to a committee aide.

Zebley was Mueller’s chief of staff when Mueller was FBI director, and he played largely the same role inside the special counsel’s office. He and another top deputy, James Quarles, had been helping Mueller prepare for his testimony in unused office space at the WilmerHale law firm, which Mueller left to lead the special counsel investigation.

“The special counsel’s office has made it clear for some time, they’d like to have him present, they would like to allow him to answer questions,” said House Intelligence Committee Chairman Adam B. Schiff (D-Calif.). “We want this hearing to be about Director Mueller.”

That sudden change to the witness list has Republicans crying foul up and down Pennsylvania Avenue. Jim Jordan began complaining yesterday afternoon; last night Donald Trump blew up on Twitter about it, and was still at it this morning:

Ranking Judiciary member Doug Collins attacked Jerrold Nadler over the violation of House rules in adding Zebley:

Republicans decried the move as an 11th-hour trick, arguing Democrats would have had to announce another witness days ago under traditional procedures in the House. In a statement Tuesday afternoon, Rep. Douglas A. Collins (Ga.), the top Republican on the Judiciary Committee, accused the chairman, Rep. Jerrold Nadler (D-N.Y.), of “again allowing the committee’s business to devolve into chaos.”

“If true, the chairman’s unprecedented decision to allow a witness’s counsel to both advise him privately and simultaneously testify alongside him shows the lengths Democrats will go to protect a one-sided narrative from a thorough examination by committee Republicans,” Collins said. “ . . . A last-minute addition to the witness list would now jeopardize whether tomorrow’s hearing complies with the rules of the House.”

That might have been why Nadler ended up keeping Zebley from testifying in the first hearing, but still nerves are on edge over the change. Why does the addition of Zebley as a witness spark so much ire? Two weeks ago, the Department of Justice attempted to discourage two members of Mueller’s special-counsel team from testifying before House committees, especially Judiciary. One was James Quarles, and the other was [wait for it] Aaron Zebley. This looks like Mueller’s attempt to either get around the DoJ or stick a thumb in its eye by demanding Zebley’s presence.

Even so, it’s not clear what impact Zebley will actually have today. He’s not going to contradict Mueller’s report and suddenly produce evidence of Russian collusion when Zebley testifies before Schiff’s committee. (That would be more of a Law & Order: SVU episode.) That would make Mueller look like an idiot for having issued a report with the opposite conclusion, and Mueller didn’t bring Zebley along to make himself look incompetent. Zebley’s role in the first hearing with the Judiciary Committee won’t involve testimony at all, and Mueller doesn’t need much help in keeping his mouth shut.

Zebley’s a wild card, even if a limited one. It might help stoke the drama, but only for those paying much attention. As The Atlantic reminded readers yesterday, that’s a small subset of American voters, and even a small subset of engaged voters:

Democrats had wanted Mueller to testify soon after he finished his investigation in April, but the special counsel’s reluctance to submit himself to what will likely turn into a partisan spectacle led to a delay. The leaders of the judiciary and intelligence committees spent weeks trying to negotiate a voluntary appearance by Mueller before ultimately resorting to a subpoena. His testimony comes after yet one more delay—a one-week postponement so that the Judiciary Committee could have an extra hour of Mueller’s time that will allow all of its members to question him. Junior lawmakers on the panel had protested the original two hours the committee was due to have, which meant the hearing would likely have ended before several of them got a chance to speak.

Rather than building suspense, the lag time seems to have had the opposite effect—like air slowly leaking out of a balloon. And if anyone popped that balloon, it was Mueller himself. On May 29, in his lone public appearance of the past two years, a televised press conference that lasted for about 10 minutes and featured no questions, the former FBI director made clear that he did not want to testify and that if he did appear before Congress, he “would not go beyond the report.” “The report is my testimony,” Mueller said.

It’s probably going to be Zebley’s too. After all, the same letter that Mueller requested from the DoJ as cover for his refusal to go beyond the report would also apply to Zebley. And that again makes Zebley’s last-minute addition a head-scratcher. If he’s not there to go beyond what Mueller will say and what’s in the report, why bother at all?

The hearings will be under way by the time this post goes live — assuming something in Washington DC actually starts on time — but we’ll keep our eyes and ears peeled for any news that emerges. We won’t necessarily be live-blogging the testimony, because if Mueller performs as he’s promised, the live blog was released about three months ago.

Update: I won’t be live-blogging this much, but it’s worth noting that Mueller made it explicitly clear that he would not be revisiting his decision not to decide on obstruction issues, nor would he comment on the open investigation into the origins of the FBI probe. In fact, Mueller reiterated, “The report is my testimony, and I will not go beyond it.”

Well, that’s going to make for a dull day.

Update: Jeff Dunetz has Mueller’s entire opening statement.