President Trump in the Oval Office in December 2017. (Jonathan Ernst/Reuters)

At long last, the House Ways and Means Committee and its chairman, Rep. Richard E. Neal (D-Mass.), have filed a lawsuit seeking to have the courts force the Trump administration do what it has refused to do: Turn over President Trump’s tax returns, as is required by law.

But why has it taken so long?

And will the public ever end up learning what it is that the president has tried to keep hidden for so long?

The answer to that second question may be: Never.

Which raises another question: Has Trump basically succeeded in killing this basic norm of transparency, at least as long as he’s in office?

Democrats won control of the House in 2018, in part, on a vow to impose accountability on a lawless, out-of-control president. Key to this was the effort to get Trump’s tax returns, which he has kept secret, in contradiction of half a century of presidential practice.

In the new lawsuit, Democrats are invoking the law which states that if the chair of a tax-writing committee requests an individual’s tax returns, the treasury secretary “shall" furnish them. The law doesn’t require the invocation of any purpose in making the request.

But in their filing, Democrats went out of their way to offer such a purpose. They noted that they are investigating whether the Internal Revenue Service is properly auditing the president’s tax returns.

To be clear, there are plenty of legitimate legislative purposes for seeking Trump’s returns. To name just two, there is an ongoing controversy about Trump’s plain violation of the emoluments clause; his tax returns would enable Congress to understand the extent of that violation — and perhaps legislate in response.

Separately, Trump has extensive overseas holding and projects, which sometimes collide with U.S. foreign policy objectives. It is vital for Congress to understand such entanglements and who might have leverage over the president, or how they might create conflicts of interest.

Regardless, Democrats have settled on their rationale, and now this goes to the courts. But the timing is a real issue.

How long will it take?

During an interview, Rep. Lloyd Doggett (D-Tex.), a member of the Ways and Means Committee, said he worries that the battle over Trump’s tax returns may not be resolved until after this term in Congress — which is to say, until after the 2020 presidential election.

“Waiting inexplicably until July to file this action just means we don’t get them this year," Doggett told us, noting that the case would have to work its way through District Court, the D.C. Court of Appeals and, finally, to the Supreme Court.

“Indeed, it will be very close as to whether we can get them in this term of Congress,” Doggett continued. "I hope we get them next year, but that’s uncertain.”

Brianne Gorod, chief counsel to the Constitution Accountability Center, told The Plum Line that House Democrats can take additional steps to get the courts to move faster. She noted that the complaint does an “excellent job” arguing for why it’s important to resolve this fast, but said that if the courts drag their feet, Democrats should continue to “urge the court to move quickly.”

“Here, Congress has a very good argument that the courts should expedite this," Gorod said. “It’s Congress attempting to exercise its oversight authority."

Gorod and another legal expert — Brian Galle, a law professor at Georgetown University — told The Plum Line that they believe Democrats are on very solid legal ground, and would likely prevail. “The only question is how long a court lets the administration illegally defy Congress,” Galle said.

But if Democrats do prevail, when do the rest of us learn what’s in Trump’s returns?

It’s unclear. Under the law, the committee can’t release them. But Galle says the relevant statute allows for the committee to “submit” them to the House or Senate, “which is in effect to make them publicly available.”

Of course, given Neal’s tendency to move very deliberately — to put it charitably — the committee would want to review the returns for some time before that happened. So who knows when it might?

Daniel Hemel, a law professor at the University of Chicago, says there’s a second possibility — take advantage of the Constitution’s speech or debate clause.

“A member of the Ways and Means Committee who obtains Trump’s returns as a result of the lawsuit could read them line by line during a committee meeting or a floor session, with no legal consequences," Hemel said. “I would be surprised if this happens, but there is precedent: Mike Gravel and the Pentagon Papers.”

At the end of the day, we all know Trump’s tax returns will likely contain major revelations. The only question is whether they will show Trump’s dealings to be merely profoundly unethical or actually criminal.

But for all practical purposes, Trump may have successfully killed this norm of transparency, at least as long as he’s president. It may require Democrats to undo this damage — if a Democrat wins the presidency after releasing her returns, for instance, or even better, if that Democratic president and a Democratic Congress codify changes to the law requiring major-party candidates to release them.

After all, the goal here isn’t just to get to the bottom of Trump’s corruption. It’s also to maintain the proper functioning of a system that will exist beyond his presidency. The new lawsuit is definitely a step in the right direction. But it remains to be seen how far it goes in undoing Trump’s deeper degradations.

Read more:

Catherine Rampell: We don’t know what Trump’s tax returns are hiding. But the hints are troubling.

Paul Waldman: Trump is counting on his hacks to keep his tax returns secret

Alexandra Petri: Some math problems for Donald Trump’s tax returns