President Trump accused special counsel Robert Mueller of being biased in his investigation into Russian interference in the 2016 election in an interview on "Fox & Friends" on June 23. (Peter Stevenson/The Washington Post)

Whenever he comments on special counsel Robert Mueller’s investigation of the Russia scandal, President Trump seems consumed with refuting the accusation of “collusion” between himself or his campaign and the Russian government (if you can call “Nuh-uh, fake news!” a refutation). But while it would certainly be shocking to learn that Trump personally conspired with Vladimir Putin to coordinate the Russians’ efforts to undermine Hillary Clinton in 2016, collusion is only one sliver of the problem he could face.

There’s a good chance that there were many kinds of wrongdoing going on around Trump, and if there were, Mueller and his team will probably find them. Which is why this investigation could become much bigger than most people realize.

Over his career — before he ran for president but continuing once his campaign was underway — Trump managed to assemble around himself a group of shady characters worthy of the most notorious mob boss, and that has continued into his presidency. Today we learn this, courtesy of Tom Hamburger and Rosalind Helderman:

A consulting firm led by Paul Manafort, who chaired Donald Trump’s presidential campaign for several months last year, retroactively filed forms Tuesday showing that his firm received $17.1 million over two years from a political party that dominated Ukraine before its leader fled to Russia in 2014.

You may recall that last year a ledger emerged in Ukraine showing huge cash payments from the party to Manafort. At the time he claimed it was a fabrication, but payments noted in the ledger were later confirmed to have taken place. And now — just as former national security adviser Michael Flynn did with regard to his work for Turkey — Manafort is retroactively registering as a foreign agent, which is the kind of thing you do when your lawyer tells you that you’re in serious trouble.

Mueller is taking a good hard look at Flynn and Manafort, but they’re just two of the grifters and con artists who have always been drawn to Trump like iron filings to a magnet. To take one colorful new example, Trump recently hired Jay Sekulow to represent him in the Russia matter, even though Sekulow’s legal specialty is First Amendment religion cases. Sekulow, it turns out, presides over a network of “nonprofits” that gets tens of millions of dollars in small contributions from conservatives, then shovels much of that money to him and his family. As Aaron Davis and Shawn Boburg report, over five years,

$5.5 million was paid directly to Sekulow and five family members in salary or other compensation, tax records covering those years show. Another $7.5 million went to businesses owned by Sekulow and his sister-in-law for producing and consulting on TV, movie and radio shows, including his weekday program, “Jay Sekulow Live!” And $21 million went to a small law firm co-owned by Sekulow, records show.

That’s not to mention the private jet. Sekulow isn’t alleged to be part of the Russia scandal, and his grift is a common one in the conservative political world. But it’s an illustration of the kind of people Trump associates with.

Which is why you may not appreciate just how broad the special counsel’s investigation could get. You may be asking, “If Trump or people around him had committed crimes, wouldn’t we have known about it by now?” After all, there have been hundreds of journalists writing about him for a couple of years now. But here’s what’s different. In many cases, those journalists would investigate a story, write it up and then move on. So you as a reader might encounter one provocative tale of, say, Trump getting large amounts of funding for real estate projects from Russian oligarchs connected to alleged mobsters — but you probably wouldn’t hear about it again. You might see a story about a mid-level Russian bureaucrat with a $75,000-a-year salary who somehow managed to buy nearly $8 million in condos from Trump. “That sounds fishy,” you’d say, but then you’d become more worried (quite appropriately) about Republicans slashing Medicaid and causing 22 million people to lose their health coverage.

But Robert Mueller isn’t going to forget, or move on to another story he has to report, or give up when things get confusing. He and his team can investigate these connections, events and relationships until they figure out what’s really there. In many cases, it might amount to nothing. But if there were crimes committed, he has the resources and authority to find out.

And it’s important to remember that if Mueller does find evidence of crimes, he can and will pursue them whether or not they have any specific relationship to the 2016 campaign. Once he begins tugging on these strings, who knows what will be discovered — about Trump’s activities before becoming president, about what his associates have done, and about anything else. Mueller can go wherever the evidence leads. Which may be why one Trump associate after another, from his personal lawyer to his son-in-law, is lawyering up.

This investigation may start with questions specifically related to the 2016 campaign and obstruction of justice, but it will almost inevitably get wider and wider. For instance, the question “What was the nature of Jared Kushner’s contacts with Russia?” leads to “What are Jared’s financial connections to Russia?,” which leads to “What’s up with that $285 million loan Kushner’s company got just before Election Day?”

Again, it may all come to nothing. It may be that everyone around Trump, including the president himself, acted with only the highest ethical standards and respect for the law. But one question leading to another is why the investigation may end up uncovering a range of wrongdoing that doesn’t actually have anything to do with politics. The political matters — potential obstruction of justice on Trump’s part, communications between Trump associates and Russia during the campaign, the full scope of the Russian project to get Trump elected — could produce evidence of wrongdoing or even crimes. But that’s only the beginning.