The Justice Department has been investigating President Joe Biden’s son Hunter Biden for a long time. The probe began in 2018, before the elder Biden even decided to run for president. It is now in its fifth year. Hunter Biden has not been charged with any wrongdoing. The investigation continues.

What has taken so long? We’ve all heard about the younger Biden making millions from shady business associations in Ukraine, China and other countries. He didn’t pay taxes on much of it, and only paid his tax bill when a new friend in Hollywood, Kevin Morris, who also just happens to be a big donor to Joe Biden’s campaign, stepped in to pay the back taxes — about $2 million — as well as Hunter’s sky-high living expenses. The idea was that Morris’ largesse would allow Hunter to say to the Justice Department: “Look, I paid my taxes. I’m clean. Let’s move on.”

Hunter Biden also retained a new, high-powered legal team, plus an aggressive public relations team, and in January, the New York Times reported that the Justice Department, in the person of the U.S. attorney in Delaware, David Weiss, was moving toward letting Hunter off easy. From the Times, on Jan. 11: “Mr. Weiss, people familiar with the investigation say, appears to be focused on a less politically explosive set of possible charges stemming from [Biden’s] failure to meet filing deadlines for his 2016 and 2017 tax returns, and questions about whether he falsely claimed at least $30,000 in deductions for business expenses.”

That’s a slap on the wrist! What a deal! If the leak was true — and who knows exactly what path it took into the New York Times — then Hunter Biden was heading toward a very happy ending to his corruption investigation. The probe would take years and years and then … fizzle out.

How exactly might that happen? Now there is a new story that could help explain what has been going on. A whistleblower has emerged from inside the Internal Revenue Service, which has been working with the Justice Department on the Hunter Biden investigation. The whistleblower is a career IRS criminal supervisory special agent who has retained a lawyer and written a letter to Congress claiming the Biden administration is interfering with the investigation into the president’s son.

The anonymous special agent retained a lawyer, Mark Lytle, who took the matter to the inspectors general of both the IRS and the Justice Department. Now, Lytle has written to the Republican and Democratic leaders of the House and Senate tax and judiciary committees. According to the letter, the special agent can detail “examples of preferential treatment and politics improperly infecting decisions and protocols that would normally be followed by career law enforcement professionals in similar circumstances if the subject were not politically connected.” The special agent can also tell about “clear conflicts of interest” as well as possible false testimony to Congress about the case.

Now the whistleblower wants to tell the story to Congress — but only if he can secure the “appropriate legal protections.” “Despite serious risks of retaliation,” Lytle wrote, “my client is offering to provide you with information necessary to exercise your constitutional oversight function.” In addition, Lytle said, the special agent wants to give information to Congress “in a non-partisan manner,” which is why the letter was sent to both Republican and Democratic lawmakers.

It would be an understatement to say that Republicans on the Hill gave the whistleblower letter a positive reception. It’s a “game changer,” Senate Judiciary Committee member Lindsey Graham told Fox News recently. “This is somebody in the IRS at a high level who apparently is willing to come forward to tell Congress that during the investigation of Hunter Biden, there was obstruction, there was a thumb on the scale to the point that they feel they need to let the Congress know if this is true. And I don’t know yet, but if this is true, if the Department of Justice yet again puts their thumb on the scale politically, then all hell is going to break out and there will be hell to pay.”

It should be said that Graham can be a big talker, but there is no doubt that if the whistleblower’s allegations — whatever they are — are both true and significant, they could make big waves in the Hunter Biden investigation, which House Republicans frequently point out is really a Joe Biden investigation. Realizing the risk, some Democrats are cautiously saying they want to know more about the whistleblower’s story.

What else could they say? Three years ago, Democrats went to the barricades to defend an anonymous CIA employee who filed a legally baseless whistleblower complaint against then-President Donald Trump in the Ukraine matter. It was legally baseless because there is no legal process for filing a whistleblower complaint against the president of the United States. There is no inspector general, no supervisor, who has the authority to investigate the president.

Nevertheless, House Democrats embraced the whistleblower and his complaint all the way to Trump’s first impeachment. They did that because they could; in the House of Representatives, the majority can do what it wants. Now Republicans have the majority in the House, and another whistleblower escapade could be coming into view.

This content originally appeared on the Washington Examiner at washingtonexaminer.com/opinion/the-hunter-biden-whistleblower.