Blumenthal on Tuesday said the lawsuit has drawn at least 196 Congressional plaintiffs. No Republicans have joined the legal action but are invited, Blumenthal said.
The Democrats involved argue Trump is violating the U.S. Constitution's Emoluments Clause by profiting from business deals involving foreign governments and continuing to do so without the consent of Congress.
During a call with reporters, Blumenthal said Trump has "repeatedly and flagrantly violated" the Emoluments Clause. Blumenthal said Trump has "never sought the consent of Congress" for profits received in deals in more than 20 countries where his businesses operate.
The Emoluments Clause of the Constitution says no person holding a federal office of profit or trust shall -- "without the Consent of the Congress" -- accept any "present, emolument, (or) office ... from any king, prince or foreign state."
Although the president holds a federal office of "trust," the clause does not name the president specifically, unlike other clauses in the Constitution -- which has generated division over interpretation. The Supreme Court has not yet ruled whether the Emoluments Clause applies to the president.
Blumenthal said Democrats believe Trump "must either sell his vast holdings ... or he must tell us and disclose now" all the benefits he receives from foreign governments. The Democrats also want access to Trump's tax returns and business records.
The lawsuit by Democrats follows a similar lawsuit filed by attorneys general in Maryland and the District of Columbia also alleging Trump is violating the Emoluments Clause. The legal action cites his hotels, golf courses and other commercial properties, including Trump International Hotel in Washington, D.C.