Democratic lawmakers are suing U.S. President Donald Trump over foreign money flowing into his global business empire.

Almost 200 senators and representatives are plaintiffs in a lawsuit alleging Trump is violating the so-called emoluments clause of the Constitution. It's being filed early Wednesday in U.S. District Court for the District of Columbia, the lawmakers said.

From January: How Donald Trump plans to avoid conflict of interest with his business empire

The plaintiffs argue they have standing to sue because the clause says only Congress may approve foreign gifts and payments.

"The framers gave Congress a unique role, a unique right and responsibility," said Senator Richard Blumenthal, a Connecticut Democrat who helped organize the lawsuit.

3rd lawsuit of its type

Although Trump turned over control of his real estate development, management and marketing company to his adult sons and a senior executive, he did not divest from it. That means he stands to benefit financially from the Trump Organization's profits, including from foreign governments.

Since he's become president, the Trump Organization has secured dozens of potentially valuable patents, including in China, and collected fees from lobbyists working for Saudi Arabia and other countries using his properties.

The new suit — the third of its kind — says the full scope of foreign payments to the Trump Organization cannot be known because the president has not made public his tax returns.

Earlier this week, two Democratic attorneys general filed a similar claim. Days after Trump's inauguration in January, a liberal-funded government watchdog filed an emoluments lawsuit. A restaurant group and two individuals in the hotel industry later joined as co-plaintiffs.

Trump calls lawsuits baseless

Trump and the Justice Department have called these lawsuits baseless. They argue the clause isn't intended to prevent normal business such as hotel payments and real estate transactions.

Representative John Conyers, a Michigan Democrat, said he and Blumenthal have amassed the "greatest number of congressional plaintiffs on any lawsuit against a president." He said they're taking the action "not out of any sense of pleasure or partisanship but because President Trump has left us with no other option."

Ahead of the filing, only Democrats were asked to sign on, but Blumenthal and Conyers plan to send letters to their Republican colleagues Wednesday asking them to join the effort.