In theory, Donald Trump shouldn’t have much to fear from Robert Mueller’s pending testimony on Capitol Hill. He’s been cleared of wrongdoing in the Russia probe by his Department of Justice toady William Barr, and Democratic brass has indicated they have no interest in impeaching him. Nevertheless, in recent days Trump has made plain his alarm at the notion, tweeting over the weekend that Mueller “should not testify.” So what’s he so afraid of?

Obviously there’s the risk that Mueller, who’s contested Barr’s framing, will demolish the convenient smoke screen the attorney general has constructed for him. But according to an Associated Press report Monday, Trump’s anxiety about a potential Mueller testimony is as much about optics as it is about substance. White House officials and other Trump allies told the outlet that the president has been grousing for days about the media coverage the special counsel’s House testimony could elicit, worried that putting Mueller on the stand would draw even more eyes than the much-watched testimony of his former fixer Michael Cohen.

He may be right to fret. In addition to opening up new lines of Democratic inquiry into Trump’s conduct, Cohen’s testimony weakened the president’s standing in the public eye. Mueller might not add anything new to his 400-odd page report, but White House officials reportedly worry that his “gravitas would add weight to some of the politically damaging and embarrassing material” about Trump. It’s one thing for Mueller to write that Trump undertook a number of harebrained schemes to subvert the Russia probe, but was essentially prevented from doing so by his insubordinate staff. It could be something else entirely to hear the measured Mueller, who has not made a public utterance since taking over the F.B.I.’s investigation into Moscow’s election meddling two years ago, detail those obstruction efforts on live television.

That’s especially true considering an overwhelming majority of Americans do not appear to have read the report, and may have been swayed by Barr’s misleading summary to Congress in March, as well as his pro-Trump spin in a bizarre press conference before the report was published. A poll released Monday suggests that Americans remain pretty split on the Russia probe since the Mueller report dropped. Could that change with the special counsel’s testimony?

It’s unlikely that Trump’s core supporters will be swayed by anything Mueller has to say. Indeed, any appearance by Mueller on the Hill would probably play out like other high-profile hearings of the Trump era: Democrats will tease out damaging information, while Republicans will defend their party leader and attack the subject of the hearing, with varying degrees of success. Still, such a testimony could weaken Trump just enough to hurt his chances heading into 2020, where Democrats—unwilling to risk a failed impeachment effort—have staked their hopes of ousting him. Polls suggest the president’s approval rating took a hit after the damning Mueller report was released. Trump and those around him seem to be afraid that the media circus around a televised hearing could be even worse for him.

But they may not be able to stop it from happening. While Barr could bend to Trump’s whims and seek to block Mueller from testifying while the special counsel is a D.O.J. employee, he won’t have that power when Mueller is once again a private citizen. It isn’t even clear if there’s appetite beyond the West Wing to block the testimony anyway; Barr has previously said he’s fine with Mueller appearing, and even some Republicans back the idea, seemingly under the belief that the special counsel will vindicate the president publicly. “I think Mueller should testify,” Doug Collins, the top Republican on the House Judiciary Committee, told Politico on Monday. “There was no collusion, no obstruction, and that’s what Bob Mueller will tell everyone.”

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