What can Mueller do if he finds evidence of criminality involving the president? He can and will (as authorized by Department of Justice regulations) file a report on his findings with the attorney general (or, since Attorney General Sessions is, in this case, recused, with the deputy attorney general, Rod Rosenstein). Rosenstein will then be faced with the important decision of whether and how to make that report public—whether to convey it to Congress or not; whether to release it publicly or not. The regulations are so vague (they say only that he “may determine that public release of these reports would be in the public interest, to the extent that release would comply with applicable legal restrictions”) that they, in effect, give Rosenstein plenary discretion to do whatever he thinks is in the best interest of the country.

So, every time you read about the threat to fire Mueller, remember this—the critical actor in most future scenarios is not Mueller, but Rosenstein. Knowing Rosenstein personally, I have high confidence that he will make what he thinks is the best decision for the country—the same may not be true of his replacement (or of the replacement attorney general, should Sessions be fired). That, of course, is why the highly dubious “secret memo” prepared by House Republicans reportedly targets Rosenstein—even though he is a Trump appointee who advocated firing Comey, Trump supporters fear he will follow the rule of law.

But what of the substance of the obstruction charge? Are pundits right that the case against Trump is becoming stronger—even if as a legal matter the president may not be charged?

Again, color me skeptical.

Collateral cases, like those involving obstruction and perjury, are ones that involve derivative offenses, not the principal charges under investigation. Proving them often turns on proof of intent. You have to show that the defendant acted with the purpose of obstructing an investigation. That means these cases tend to rise or fall on the strength of the case proving the underlying crime. It matters very much to juries and the public that we know exactly what it is that a defendant is covering up. If we don’t think it matters that much (as many in America seem to have concluded when confronted with President Clinton’s sexual conduct) or that it hasn’t been proven, then the cover up is often forgiven.

In the Trump investigation, we have yet to determine whether the campaign was involved in an underlying crime of electoral manipulation involving Russia, much less how the broader American public thinks of it. Many, like me, see strong evidence of Russian interference in the American election system and good evidence (though less strong) that some in the Trump campaign willingly accepted this and sought to take advantage of it. But candor compels the recognition that evidence of President Trump’s personal involvement is much thinner than, say, that of his son-in-law and other campaign staff.