The House sued the Treasury Department and the Internal Revenue Service on Tuesday, demanding access to President Trump’s tax returns and escalating a fight with an administration that has repeatedly dismissed as illegitimate its attempt to obtain the financial records.

The lawsuit moves the dispute into the federal courts after months of sniping between the Democratic-led House Ways and Means Committee, which requested and then subpoenaed the returns, and Treasury Secretary Steven Mnuchin. The case may ultimately go to the Supreme Court, and its outcome is likely to determine whether financial information that Mr. Trump has kept closely guarded in spite of longstanding presidential tradition will be viewed by Congress and, ultimately, the public.

In Tuesday’s filing, the House argued that the administration’s defiance of its request amounted to “an extraordinary attack on the authority of Congress to obtain information needed to conduct oversight of Treasury, the I.R.S. and the tax laws on behalf of the American people.” It asked a judge to order the defendants to comply.

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In almost every instance, the Trump administration has argued that Congress’s power to gain access to those materials is inherently limited to information that would serve “legitimate” legislative purposes — defined by the executive branch to be limited to materials needed to help draft new laws and to exclude uncovering potential wrongdoing.

Congress retorts that its powers to compel information are far more sweeping than that and encompass oversight of important matters in general — and that its decisions about what information it wants to subpoena are not to be second-guessed by the White House.

The same dispute is at the center of a pair of lawsuits over subpoenas to accounting and banking firms for other financial records involving the Trump Organization. So far, two Federal District Court judges have swiftly rejected the argument offered by Mr. Trump’s private legal team that those requests did not carry legitimate legislative purposes. Mr. Trump has taken those losses to appeals courts.

There is a clear statutory case for getting Trump’s tax returns, as well as decades of court precedent on the role of Congress investigating the executive, but this should have gone to court on Day 1, because this will make it all the way to the Supreme Court, which takes time.

I’m not particularly sanguine about Congress’s chances in the Supreme Court, at least 4 of the justices would rule in favor of the White House under the theory that it’s OK if you are a Republican, but if they had filed suit earlier, it would get there sooner.