Reuters/Joshua Roberts (Joshua Roberts/Reuters)
Opinion writer

One of the enduring mysteries of Trump fandom is that to this day, many of the president’s supporters continue to believe that he is a sworn enemy of “the swamp,” a corrupt system in Washington that he is busily cleaning up. Perhaps it’s too much to ask for a group of voters to admit that one of the central promises their champion made was a lie from the beginning.

But the corruption of the Trump administration is so comprehensive and wide-ranging that it contains important — and depressing — lessons about how corruption works and why it is so difficult to eradicate.

Some facets of Trump corruption are new and unique. For instance, for two centuries nobody thought much about how the emoluments clause of the Constitution should be understood, because the idea that any president would use his office for personal financial gain was absurd. But then there are Trump administration scandals that sound extremely familiar:

The Transportation Department under Secretary Elaine Chao designated a special liaison to help with grant applications and other priorities from her husband Mitch McConnell’s state of Kentucky, paving the way for grants totaling at least $78 million for favored projects as McConnell prepared to campaign for reelection.

Chao’s aide Todd Inman, who stated in an email to McConnell’s Senate office that Chao had personally asked him to serve as an intermediary, helped advise the senator and local Kentucky officials on grants with special significance for McConnell — including a highway-improvement project in a McConnell political stronghold that had been twice rejected for previous grant applications.

This comes on the heels of news that Chao tried to include members of her family, which owns a large shipping firm that does extensive business in China, in official meetings with the Chinese government. If there’s anything unusual about these stories it’s that Chao was one of the few people in Trump’s Cabinet who actually knew their way around government; among other things she was secretary of labor under George W. Bush. As someone who had been a member of the Washington elite before Trump arrived and will remain so after he departs, she might have been a less likely suspect for corruption.

But this particular kind of corruption — a federal department steering grants to a particular area not solely on merit but because of the political interests of the secretary (or in this case, her husband) — is by today’s standards utterly mundane. It’s certainly wrong, but it’s usually not the kind of thing anyone goes to jail for.

But it is probably the kind of thing Trump’s voters thought he would be cleaning up when he told them he’d “drain the swamp.” What they didn’t realize was that he couldn’t care less. Do you think Trump is concerned that government contracts are awarded fairly? Of course not. If this helps Mitch McConnell get reelected, he’s all for it.

And here’s another story from Monday:

A real estate company part-owned by Jared Kushner has received $90m in foreign funding from an opaque offshore vehicle since he entered the White House as a senior adviser to his father-in-law Donald Trump.

Investment has flowed from overseas to the company, Cadre, while Kushner works as an international envoy for the US, according to corporate filings and interviews. The money came through a vehicle run by Goldman Sachs in the Cayman Islands, a tax haven that guarantees corporate secrecy....

His holding is now valued at up to $50m, according to his financial disclosure documents.

Let’s not forget that Kushner is allowed to work in the White House in the first place because in the early days of the Trump presidency the Justice Department issued a document stating that anti-nepotism laws don’t apply to the White House staff. He had his application for a security clearance rejected by career officials “because of concerns about foreign influence, private business interests and personal conduct,” though they were overruled by a political appointee.

As The Post reported last year, “Officials in at least four countries have privately discussed ways they can manipulate Jared Kushner” by “taking advantage of his complex business arrangements, financial difficulties and lack of foreign policy experience.”

So shadowy foreign interests are providing funding to a firm in which Kushner’s personal interest is estimated at $50 million? Add that to his list of sketchy financial entanglements, such as the case of the financial services company with connections to the Qatari government that bailed out Kushner’s family business from its disastrous investment in 666 Fifth Avenue, an investment that nearly destroyed the Kushner Companies.

In tandem, these stories highlight one of the sobering lessons of the past few years: It’s easy to make the system dirtier, and really hard to make it cleaner. If he wants to, a president can try to change some rules and act with integrity himself, but if the next president is a crook, what the previous president did or didn’t do won’t constrain him at all. He’ll be able to be nearly as corrupt as he wants.

Barack Obama, for instance, came into office with a lot of high-minded ideas about transparency and good government. He put many of them into practice, making it harder for lobbyists to join the administration and easier for the public to access information, and running an administration that turned out to be remarkably free of scandal.

But if you ask people who really understand how government works whether the Obama years made a fundamental and lasting difference in how the system operates, they’ll say, “Well … not really.” It’s not that much of what he did wasn’t worthwhile, it’s just that in the end it either turned out to be not as transformational as people hoped, or it was easily reversed once Trump took office.

So what happens once Trump is gone? Unless we literally put the leader of the Russian mafia in the Oval Office, the next president will be less corrupt than this one. Nevertheless, the danger is that Trump will have succeeded in normalizing his own behavior, whether it’s appointing family members to key offices, maintaining financial interests that could affect policy decisions, or just trying to profit off the presidency.

We can hope that things get better, and they might. But it may be hard to bring us back even to where we were before in terms of the level of government corruption — which wasn’t that great to begin with.

Read more:

Greg Sargent: Trump’s latest rage-threat gives Democrats a big opening. One just took it.

E.J. Dionne Jr.: Give Trump an ultimatum on his stonewalling

Jennifer Rubin: Forget impeachment. Tee up prosecution.

E.J. Dionne Jr.: Dear Robert Mueller: Your report can’t speak for itself

Max Boot: Here are seven reasons Trump should be impeached