Article has straight out admission of major Constitutional agenda:

Racine [ D.C. Attorney General Karl A. Racine (D) ] said he felt obligated to sue Trump in part because the Republican-controlled Congress has not taken the president’s apparent conflicts seriously.

“We’re getting in here to be the check and balance that it appears Congress is unwilling to be,” he said. “We’re bringing suit because the president has not taken adequate steps to separate himself from his business interests.”

and explanation of same:

Norman Eisen, who served as White House ethics lawyer for President Barack Obama and is CREW’s board chairman, said jurisdictions such as the District and Maryland are among the “most perfect plaintiffs” to sue over emoluments because they have a coequal say in making sure the Constitution is being enforced.

“In the emoluments clauses, we have these ancient air bags that were placed in the Constitution by the framers that are now being deployed,” said Eisen, who has been advising the District and Maryland on their suit. “Trump is the framers’ worst-case scenario; a president who would seize office and attempt to exploit his position for personal financial gain with every governmental entity imaginable, across the United States or around the world.”

The suit will allege that Trump has taken favors from the U.S. government. It will argue that the U.S. General Services Administration wrongly allowed Trump’s company to continue to lease the Old Post Office building, where Trump built his D.C. hotel, even though a clause in the contract said no elected official could remain on the lease.

The GSA initially said Trump would have to fully divest from the hotel after the election. But after Trump proposed increasing GSA’s budget, the agency issued a letter saying Trump was in full compliance with the lease.

The suit will seek an injunction to force Trump to stop violating the Constitution, but will leave it up to the court to decide how that should be accomplished.

The suit also will allege that Trump has violated the “domestic emoluments” clause in the Constitution, creating a situation in which states feel compelled to compete for Trump’s favor, perhaps by offering zoning exemptions, waivers or other benefits to help his businesses. [....]

Politico's coverage; Reminds me did I mention they would be getting the tax returns but wouldn't be public?  Also note the Legislature of Maryland approved their power to do this:

[....] Last February, Maryland's Legislature gave Frosh the authority to sue the federal government without the approval of Gov. Larry Hogan, a Republican, or the General Assembly, currently controlled by Democrats.

The president’s tax returns, which Trump has refused to release despite a decades-long tradition of presidential candidates releasing them, will be sought through the discovery process if the case is allowed to proceed, Frosh said.

“We will be seeking the president’s financial information, including his tax returns,” the Maryland official said.

The lawsuit accuses Trump, via his businesses, of being “deeply enmeshed with a legion of foreign and domestic government actors.” His continued ownership of the Trump organizations constitutes “unprecedented constitutional violations,” the complaint says.

Even if the attorneys general were to get access to Trump's tax returns, it's unlikely the documents would be made public through this suit, since such records are typically subject to confidentiality restrictions imposed by the courts [....]