President Trump speaks to reporters about a shooting at a Pittsburgh synagogue at Andrews Air Force Base. Oct. 27. (Andrew Harnik/AP)
Opinion writer

Now that Democrats will assume control of the House of Representatives in January, it seems almost certain that among the first orders of business will be issuing a subpoena for Donald Trump’s taxes. At least, Trump and the Republicans think that sort of inquiry is coming. Trump told a Wednesday press conference he would assume a “warlike posture” if Democrats open up investigations into him.

As for Senate Majority Leader Mitch McConnell, on Wednesday he called Democratic calls for Trump’s taxes, along with other probable House investigations into Trump, “presidential harassment.” Au contraire. A public airing of Trump’s taxes is necessary, for the sake of both the integrity of the United States government and questions of national security.

All available evidence suggests Trump’s tax returns make for fascinating reading, and not in a way that would reflect well on him or his family. Last month, the New York Times documented what appeared to be financial fraud by the Trump family businesses going back decades. It’s likely that a public airing of his most recent tax returns will shed more light on that matter. They would also almost certainly reveal how much he benefited from the Republican tax reform package, which showered benefits on the wealthiest Americans while offering a few temporary crumbs to the majority of the population.

The potential corruption goes deeper than that. Questions have also recently been raised about the Trump business empire’s financial dealings with Saudi Arabia, thanks to his less-than-robust concern over the almost-certain murder of Post columnist Jamal Khashoggi by the Saudi government. This joins questions about his seeming subservience to Russian President Vladimir Putin, and whether that can be explained by the amount of Russian money that’s flowed into Trump properties over the past decade. (One investigation alone found Russians spent more than $100 million buying properties at a single Trump property in South Florida.) Then there is China, where, for all of his tough talk on tariffs, there’s evidence Trump’s taken his financial interests, as well as his family’s, into account.

But this is all just conjecture, and will be until we actually get a look at Trump’s tax returns. This is almost certainly the real reason why Trump is refusing to make them public. He claims — as recently as Wednesday’s surreal and often out-of-control press conference — it’s because he’s under audit by the IRS, and if that ever ends, he’d consider making the documents public. However, he added, a business as complex as his is under “continuous investigation” and “people wouldn’t understand them.”

This is poppycock. Sure, it’s possible Trump’s under audit — we’ve no way of knowing — but it’s absolutely untrue that would prevent him from making the documents public. As for comprehending them, there are many tax experts out there, and I’m sure more than a few will offer to help the public out.

McConnell compared any Democratic investigations of Trump to ones the Republicans pummeled Bill Clinton with two decades ago, and said they were likely to be as unpopular. That comparison is neither fair nor accurate. Republicans were attempting to impeach Clinton for lying about an affair. Democrats are attempting to find out where Trump’s money is coming from, if those sources are legal ones, and if they compromise United States interests. The response of the Republicans and Trump is to threaten to set off a constitutional crisis.

Trump’s acting like a guilty man — on Wednesday afternoon, he forced out Attorney General Jeff Sessions, who had recused himself from overseeing the Robert Mueller investigation. It seems to defy reason that he would take these sorts of actions unless there was something or somethings in these matters he and his administration believe will impact how the public views Trump. If Trump truly believed a public airing of his taxes couldn’t do him damage, it seems unlikely he would fight this hard to keep them secret. That’s why he doesn’t want to be accountable to the American public for what’s in them.

There’s no reason anyone should let him get away with this.

Read more:

George Will: America has shingles. A divided Congress could be the cure.

Jim Kessler and Lanae Erickson: Don’t let progressives fool you. Moderate Democrats have the energy to win.

Michael Gerson: Trump is leaving a trail of ruin behind him

Robert J. Samuelson: Can Trump and Congress overcome distrust? Doubtful.

Erik Wemple: Republicans lost the House, so Trump took it out on the media

The Post’s View: Trump’s rambling, angry news conference shows he ignored the message voters sent him