WASHINGTON — House Democrats have finally filed suit for President Trump’s tax returns, kicking off a new legal clash between Congress and his administration.

Trump has defied a House subpoena issued May 10 for six years' worth of his federal tax returns, arguing the request doesn’t have a legitimate legislative basis. Now, Democrats are asking a federal judge to weigh in.

The lawsuit was brought Tuesday by the House Ways & Means Committee against Trump’s IRS and Treasury Department and the chiefs of those agencies, Charles Rettig and Steven Mnuchin, respectively.

“In refusing to comply with the statute, Defendants have mounted an extraordinary attack on the authority of Congress to obtain information needed to conduct oversight of Treasury, the IRS, and the tax laws on behalf of the American people,” the lawsuit says.

Tuesday’s lawsuit represents another battlefront in the sprawling legal dispute between Trump and Congress.

House Democrats have opened multiple investigations into Trump and his family company’s finances, following allegations of impropriety by his longtime attorney and fixer Michael Cohen. Trump has responded with an unprecedented stonewalling campaign and counter-lawsuits, which could slow down Democratic investigations by months or even years.

The House Ways & Means Committee is seeking Trump’s personal and business tax returns using a little-known provision of the federal tax code known as Section 6103, which dates back a century and states that the Treasury secretary “shall furnish” requested tax returns to the committee.

In June, Trump’s Department of Justice issued a legal defense of Mnuchin’s refusal, which essentially argued that House Ways & Means chairman Richard Neal wasn’t being honest about why he wants a look at Trump’s taxes — because he really just wants to release them.

“The Chairman’s request that Treasury turn over the President’s tax returns, for the apparent purpose of making them public, amounted to an unprecedented use of the Committee’s authority and raised a serious risk of abuse,” Trump’s Justice Department wrote.

Tuesday’s decision marks a change in posture from Chairman Neal, whose reticence to go to court to enforce his request had spurred complaints from liberal activists. The group Stand Up America, in particular, targeted Neal, launching a campaign to get voters to text and email members of the Ways & Means Committee to file the lawsuit.

See you in court

While Trump’s legal strategy appears designed to bog down Democratic investigations and push any final results past the 2020 election, recent decisions suggest the process may move much faster.

In May, U.S. District Judge Amit Mehta issued a sweeping rebuke to Trump’s lawsuit to block Democrats from subpoenaing records from his longtime accounting firm, Mazars USA. Days later, another judge made a similar ruling against Trump in his bid to block Democrats’ request for documents from his longtime favorite bank, Germany’s Deutsche Bank.

Last week, another federal judge ruled in favor of Congressional Democrats in their lawsuit against Trump for allegedly violating the Constitution’s ban on receiving payments from foreign government’s while in office, saying they could begin seeking records from his family business.

All of those cases will likely be tied up further on appeal, however, and could eventually be decided by the Supreme Court, where Trump’s legal team appears to believe it’s more likely to get a sympathetic hearing than in the lower courts.

If Trump ultimately prevails at the Supreme Court in his fight to keep his tax returns secret, Democrats do have a backup option. Lawmakers in New York State have passed legislation that would allow local officials to turn over Trump’s state tax returns to Congress if Neal requests them.