It wasn’t surprising that Rudy Giuliani chose the first anniversary of Robert Mueller’s appointment as special counsel to emerge from a week of silence and give a new round of interviews. Although the former mayor says that he is acting as Donald Trump’s outside legal counsel, it’s increasingly clear that his main role is that of attack dog. His principal assignment: to bloody Mueller, and, if possible, disable him.

Speaking to Fox News’ Laura Ingraham on Wednesday night, Giuliani claimed that, after a year of investigating, Mueller “has nothing” on Trump, “which is why he wants to bring the President in for an interview.” There was “no reason for this investigation,” Giuliani went on. Referring to Mueller’s team, Giuliani added, “They have only exculpatory information . . . . So it’s about time to get the darn thing over with. It’s about time to say, ‘Enough.’ We’ve tortured this President enough.”

In other interviews, Giuliani claimed that Mueller’s team had acknowledged to Trump’s attorneys that, in deference to established legal guidance at the Justice Department, it wouldn’t bring a criminal indictment against the President, whatever its findings. “It’s as clear as can be that they don’t have the right to indict under the Justice Department rules,” Giuliani told NBC News. “And I know they’re not going to indict.” During his sitdown with Ingraham, Giuliani extended this argument, arguing that for “the same reason they can’t indict him, they can’t issue a subpoena to him.”

These statements raise an obvious question: If Mueller really has nothing on Trump, and if, in any case, he is barred from bringing an indictment or issuing a Presidential subpoena, why are the President and his attorneys so concerned about the investigation? In these circumstances, the White House’s primary aim should be to help Mueller finish up expeditiously, so he can proclaim the President innocent of collusion, obstruction of justice, or any other wrongdoing. As the Republican congressman Trey Gowdy remarked to Trump’s former lead attorney, John Dowd, after he called on Mueller to wrap it up, “If you have an innocent client … act like it.”

The real takeaway from Giuliani’s reappearance this week, which was accompanied by another “Witch Hunt” salvo from Trump, is that the White House remains deeply anxious about Mueller’s investigation, and no wonder. In the face of constant attacks from the President, his media outriders, and some Republican lackeys on Capitol Hill, the special counsel’s team has proceeded methodically for the past twelve months on at least five distinct but connected fronts: Russian trolling and voter-targeting on social-media platforms; the hacking and release of Democratic e-mails; direct contacts between members of the Trump campaign and individuals connected to the Russian government; Trump’s business dealings with people and entities connected to Russia; and possible obstruction of justice.

Mueller has also taken over and beefed up the preëxisting F.B.I. investigation of Paul Manafort, Trump’s former campaign chief, and Rick Gates, Manafort’s former deputy, which arose out of consulting work they did for a pro-Russian party in Ukraine. On top of all this, it has been widely reported that Mueller asked the Justice Department to investigate the business dealings of Michael Cohen, Trump’s private attorney. Strictly speaking, that is a separate probe. But nobody on Trump’s team doubts that, if and when Cohen decides to coöperate with the prosecutors, Mueller’s investigators will be all ears.

The timetable of the investigation is also instructive. Despite all the media attention it has received, Mueller’s team seems to have done little or no tattling to reporters. But thanks to last week’s leak of banking records related to Cohen, and the media storm that ensued, we know that, as early as last fall, Mueller’s team demanded information from some of the companies that hired the Trump fixer as a consultant after the election. This suggests that the investigation is running many months ahead of the media, and also, perhaps, ahead of the White House’s knowledge of its activities. That has to alarm Trump, as should the fact that Gates and Michael Flynn, Trump’s former national-security adviser, are already coöperating with Mueller, while Cohen and Manafort are under great pressure to flip.

Another thing we know, courtesy of a leak to the Times by Trump’s lawyers, is that Mueller wants to pose at least forty-nine questions to the President himself. Despite Trump’s constant refrain that there was no collusion with Russia, many of these questions also relate directly to what happened before the 2016 election. Here’s a sample: “During the campaign, what did you know about Russian hacking, use of social media, or other acts aimed at the campaign?” and “What knowledge did you have of any outreach by your campaign, including by Paul Manafort, to Russia about potential assistance to the campaign?”

It is perfectly possible, of course, that Mueller’s probe doesn’t have any evidence against Trump. It is also possible that it does. The thousands of pages of interview transcripts that the Senate Judiciary Committee released this week raised anew the question of whether Donald Trump, Jr., told his father about the infamous meeting with four Russians at Trump Tower on June 9, 2016. The participants in the meeting insist that it didn’t lead anywhere, but, as I noted earlier this week, the intent, at least on the part of Donald, Jr., was relatively clear.

So far, no one from the Mueller team has confirmed Giuliani’s claim that the special counsel has ruled out bringing an indictment against Trump, but there may be some truth to it. Twice in the past forty years, the Office of Legal Counsel at the Justice Department has opined that a sitting President can’t be indicted. And in the appointment letter that Rod Rosenstein, the Deputy Attorney General, issued to Mueller, he referred explicitly to certain sections of the Code of Federal Regulations, which say, “A Special Counsel shall comply with the rules, regulations, procedures, practices and policies of the Department of Justice.”

But the Justice Department rulebook doesn’t entirely prohibit the possibility of Mueller diverging from standard practice. It also says: “Should the Special Counsel conclude that the extraordinary circumstances of any particular decision would render compliance with required review and approval procedures by the designated Departmental component inappropriate, he or she may consult directly with the Attorney General.” This suggests that if Mueller found evidence of a serious crime involving the President, and he believed it should be prosecuted in an ordinary court of law, he could go to Rosenstein, who in this case would be the acting Attorney General—and the ultimate decision would fall on Rosenstein’s shoulders.

Most people in Washington don’t expect Mueller to bring criminal charges against Trump. If he doesn’t, and Trump doesn’t fire him before he completes his investigation, the key issue—whether or not to impeach Trump—may well be left to Congress. And since Congress operates in the court of public opinion, this would ultimately be a political decision.

That, of course, is another reason that Trump brought in Giuliani—to stick up for him and his family in public, even if that involves defending the indefensible, as Giuliani did during his interview with Ingraham. Referring to the June, 2016, meeting at Trump Tower, Giuliani said, “When I ran against [Democrats] they were looking for dirt on me every day. I mean, that’s what you do . . . . Nothing illegal about that. And even if it comes from a Russian or a German or an American, it doesn’t matter.”

Ignore, for a moment, the ethical content of this argument. Federal election statutes prohibit foreigners from contributing anything of value to a U.S. election. Dirt on a rival candidate is certainly something of value. If an American citizen assists a foreign national in breaking this law, he or she is committing a crime, too. The statutes are pretty clear on this, and Mueller has a lot of experienced lawyers working for him. In delving into this area, and the many others under investigation, we can rest assured that they won’t be put off by Giuliani’s bluster.