Former White House chief strategist Stephen K. Bannon gave a wide-ranging interview to "60 Minutes." Here's what he said about Republican leadership and the Russia investigation. (Amber Ferguson,Jenny Starrs/The Washington Post)

In an interview with “60 Minutes” that aired Sunday (though this excerpt appeared only online), former Trump strategist Stephen K. Bannon asserted that the firing of FBI Director James B. Comey was the biggest mistake in modern political history. And guess what: He could be right!

Most coverage of this has focused on the newsworthiness of Bannon questioning President Trump’s less-than-impeccable judgment. But the real news here is that Bannon’s perspective suggests that people very close to Trump believe that special counsel Robert S. Mueller III could destroy this entire presidency.

Here’s the key exchange with Charlie Rose:

BANNON: I don’t think there’s any doubt that if James Comey had not been fired we would not have a special counsel, yes.

ROSE: So we would not have the Mueller investigation.

BANNON: We would not have the Mueller investigation, we would not have the Mueller investigation in the breadth that clearly Mr. Mueller is going. … Because I think directionally it’s a very different investigation.

Keep that idea of “the breadth that clearly Mr. Mueller is going” in the back of your head. Now here’s more:

ROSE: Someone said to me that you described the firing of James Comey — you’re a student of history — as the biggest mistake in political history.

BANNON: That probably would be too bombastic even for me, but maybe modern political history.

ROSE: The firing of James Comey was the biggest mistake in modern political history.

BANNON: I think, if you’re saying that that’s associated with me, then I’ll leave it at that.

In modern political history, if we’re just sticking to presidential scandals (and not policy decisions such as George W. Bush deciding to invade Iraq), then we have some pretty big mistakes. There’s Bill Clinton’s decision to have an affair with Monica Lewinsky. There’s Ronald Reagan’s decision to sell arms to terrorists so the profits could be used to fund an illegal war in Central America. Then there are any number of decisions Richard Nixon made — authorizing a coverup of the Watergate break-in, putting a recording system in the Oval Office — that led him to resign.

If firing Comey was bigger than all of them, what does that mean? It can only mean that it could end Trump’s presidency. Anything less would make it a big mistake, but not the biggest. Bannon’s unspoken logical chain goes like this: Trump fires Comey, which leads to the appointment of a special counsel, which leads to the discovery of terribly damaging information about Trump, which brings him down, either through resignation or impeachment.

We should say that it’s possible that a special counsel would have been appointed even if Trump had not fired Comey, though it certainly made it much more likely — particularly after Trump went on national TV and said that he fired Comey in order to shut down the Russia investigation, then reportedly told the Russian ambassador and foreign minister the same thing. If that winds up becoming the core of a case that Trump committed obstruction of justice, then Bannon would be right.

Now, it’s of course possible that Bannon didn’t mean to imply any such thing. After all, Bannon also insisted in this interview that there was absolutely nothing to the Russia scandal. Even with what we know so far, that’s not true. There’s copious evidence of Russia’s efforts to manipulate our election in order to help Trump win, and at the very least we know that key members of Trump’s inner circle — his first-born son, his son-in-law and closest adviser, and his campaign manager — were eager to meet with people connected to the Russian government in the hopes that they could provide dirt on Hillary Clinton that the campaign could deploy against her. We’ll probably find out even more about what went on during the campaign.

But Bannon said something else here that is suggestive: He noted that the “breadth” of Mueller’s probe is now a lot wider than it otherwise might have been. Which means the Russia story may not be what Bannon is really worried about. He surely knows that there is equal if not more danger to Trump in the likelihood that the special counsel’s investigation will go beyond questions about the election. He’s saying that the Comey firing opened up the investigation to go into areas where it otherwise wouldn’t have.

If in the course of his investigation Mueller comes across evidence of a crime, he’s permitted and even obligated to pursue it, even if it doesn’t have anything to do with the questions about the campaign that were the initial justification for the investigation. And because investigating the Russian connection to the election requires an examination of Trump’s intricate web of financial connections with Russian interests (including a colorful collection of oligarchs and mobsters), the chances that Mueller will find something fishy or even criminal are very high indeed. No one who has carefully followed Trump’s business career believes that there isn’t some very shady stuff lurking about there.

After all, this is likely one of the main reasons Trump was willing to endure so much criticism over not making his tax returns public. Those returns, which detail the income he gets from hundreds of different sources, are essentially a gigantic pile of threads; start pulling on them one at a time and there’s no telling what you might find.

Bannon may not know where all of the bodies are buried (so to speak) in Trump’s long and varied career in real estate and casinos, or exactly why it is that Russian interests have showered Trump with hundreds of millions of dollars over the years. But he knows enough to know that if you have a special prosecutor with ample resources and authority and a team of specialists in financial crimes rooting around, they’re going to find something. Maybe a lot of somethings. And Bannon knows, or at least appears to believe, that it could bring this presidency down.