In the nearly four months since President Trump took office, many Democrats have questioned his ability to run the country. But only Rep. Jamie Raskin, D-Md., has authored legislation to address those concerns.

His bill, called the “Oversight Commission on Presidential Capacity Act” would invoke a never-before-used part of the 25th Amendment to determine if the president is capable of doing his job.

Protesters gather Thursday outside the Republican National Committee spring meeting in Coronado, Calif. About 300 protesters marched on the beach, chanting, "Hey, hey, ho, ho, Donald Trump has got to go!" Associated Press/Elliot Spagat

Raskin, a constitutional law professor, said he started thinking about the bill as soon as he was elected to his first term in November.

He said the issue has become increasingly relevant as constituents in his liberal Montgomery County district clamor for action in the Trump administration’s bumpy first months.

“This is a president who has insisted that Ted Cruz’s father was involved in the assassination of John F. Kennedy and that Barack Obama was born in Indonesia and he has uttered blatant lies and never retracted them,” Raskin said in an interview Friday. “And that is a sign of a serious mental disturbance.”

Raskin quietly filed the bill in early April, but alerted reporters to it Friday, hours after Trump, in a tweet, implied to fired FBI Director James Comey that he had “tapes” of their private conversations.

“This is a president who seems increasingly at odds with everyone and everything around him,” said Raskin, who skipped Trump’s inauguration.

In the Republican-controlled House and Senate, the bill has little chance of passing or getting a hearing, but Raskin said he filed the bill to put a framework in place in case Trump’s party turns on him.

The bill has 20 Democratic co-sponsors, including Rep. Anthony Brown (Md.) and, the District’s nonvoting delegate, Eleanor Holmes Norton, and no Republicans.

Parts of the 25th amendment that provide for temporary transfer of power from the president to the vice president have been invoked when Presidents Ronald Reagan and George W. Bush underwent surgery.

But Raskin’s bill would activate Section 4 of the 25th amendment to create an independent, nonpartisan commission to determine if the president is physically or psychologically unfit for office.