(Donald Trump via Twitter)
Opinion writer

That President Trump is boundlessly corrupt is no longer even a matter of debate; at this point, all that’s in question is how deep his corruption goes and what we should do about it. But as his many scandals unfold, one of the things becoming clear is the way Trump’s corruption spreads — through the government, through the Republican Party and in some ways through the country itself.

In both the Ukraine scandal and the emerging scandal over Trump’s tax returns, we’re seeing how even Trump’s loyal aides and advocates assume he has the worst motives and intentions, then make their own decisions accordingly.

There may be dissenters here and there, and even some who take the risk of blowing the whistle. But not even his most devoted lickspittles believe Trump wants them to act ethically and in accordance with the law and the interests of the United States.

In the case of the IRS whistleblower, we’re seeing another example of how Trump’s underlings assume the worst about him — which is never an inaccurate assumption — and then act on his desires, without needing to be told explicitly what he wants and expects. Here’s the latest:

An Internal Revenue Service ­official has filed a whistleblower complaint reporting that he was told that at least one Treasury Department political appointee attempted to improperly interfere with the annual audit of the president’s or vice president’s tax returns, according to multiple people familiar with the document.

Trump administration officials dismissed the whistleblower’s complaint as flimsy because it is based on conversations with other government officials. But congressional Democrats were alarmed by the complaint, now circulating on Capitol Hill, and flagged it in a federal court filing. They are also discussing whether to make it public.

Aside from the allegation of improper interference, we know almost no details about this complaint, other than that it alleges that “political appointees may have tried to interfere with the government audit process, which was set up to be insulated from political pressures,” in The Post’s description.

Our reporters spoke to the whistleblower himself, but he refused to discuss the substance of the complaint; instead, he spoke only about the importance of protecting whistleblowing.

But just based on the broad allegation — that Treasury Department officials attempted to interfere in the routine audit of the president or vice president’s tax returns — we can surmise a good deal about what likely went on.

Trump clearly believes that if his tax returns were ever made public, the political fallout would be catastrophic. To prevent that from ever happening, he has lied repeatedly about the matter (claiming over and over that he would soon release them when he obviously never had any intention of doing so) and filed lawsuits trying to prevent congressional subpoenas for those returns from being honored. As The Post reported in April, he has told aides “he would fight the issue to the Supreme Court, hoping to stall it until after the 2020 election.”

Just as clearly, the people who work for Trump also believe the public release of his returns would be a disaster. They have acted on that belief, taking cues from the president without ever having to be told explicitly what a critical priority keeping the returns secret is.

So for instance, Treasury Secretary Steven Mnuchin testified in May that he has never spoken with Trump or anyone else in the White House about it; he decided to violate the law and refuse to honor a congressional demand for Trump’s returns all on his own.

I believe him. I also believe that Trump didn’t have to order Attorney General William P. Barr to have the Justice Department join a lawsuit seeking to prevent investigators from getting Trump’s returns from his accounting firm. Barr, who has shown there’s almost nothing he won’t do to protect Trump, no matter how dishonest or unethical, knew just what was required.

If the whistleblower’s complaint is accurate, some official or officials in the Treasury Department decided to intervene in what is supposed to be a routine process carried out by IRS professionals. The danger presented by that audit was apparently too great. You would do that only if you feared the truth, that carrying out the audit according to standard procedures would reveal wrongdoing or perhaps even criminal behavior.

We’ll have to wait for details to understand this matter more fully. But the analogy to the Ukraine scandal is inescapable. When White House officials heard Trump’s call with the president of Ukraine, they immediately knew that if it became public, it would be a disaster, so they placed records of the call in a secure system meant to prevent access from all but a tiny number of officials. Trump didn’t order them to do it; he didn’t have to, because the stakes were obvious. That Trump had abused his office they had no doubt.

No one else does, either — not career professionals in the government, not Trump’s own aides, not the Republican officeholders leaping into elevators to avoid reporters’ questions about him, and certainly not the rest of us. We’ve all known all along. Now we have to decide if he’ll be held accountable.

Read more:

Catherine Rampell: There’s another whistleblower complaint. It’s about Trump’s tax returns.

Richard Neal: Why my committee needs the president’s tax returns

Paul Waldman: The clock is ticking on Trump’s tax returns

The Post’s View: Getting access to Trump’s tax returns is important. So is fighting for them within the bounds of the Constitution.

Greg Sargent: Trump supporters can’t make these facts disappear