President Trump, whose sometimes erratic behaviour in office has generated an unprecedented debate about his mental health, declared on Saturday that he was perfectly sane and accused his critics of raising questions to score political points, reports the New York Times.

In a series of Twitter posts that were extraordinary even by the standards of his norm-shattering presidency, Mr. Trump insisted that his opponents and the news media were attacking his capacity because they had failed to prove his campaign conspired with Russia during the 2016 presidential campaign.

“Now that Russian collusion, after one year of intense study, has proven to be a total hoax on the American public, the Democrats and their lapdogs, the Fake News Mainstream Media, are taking out the old Ronald Reagan playbook and screaming mental stability and intelligence,” he wrote on Twitter even as a special counsel continues to investigate the Russia matter.

“Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart,” he added. He said he was a “VERY successful businessman” and television star who won the presidency on his first try. “I think that would qualify as not smart, but genius….and a very stable genius at that!”

Elaborating during a meeting with reporters at Camp David later in the day, Mr. Trump again ticked off what he called a high-achieving academic and career record. He raised the matter “only because I went to the best colleges, or college,” he said. Referring to a new book citing concerns about his fitness, he said, “I consider it a work of fiction and I consider it a disgrace.”

The president’s engagement on the issue is likely to fuel the long-simmering argument about his state of mind that has roiled the political and psychiatric worlds and thrust the country into uncharted territory. Democrats in Congress have introduced legislation to force the president to submit to psychological evaluation. Mental health professionals have signed a petition calling for his removal from office. Others call armchair diagnoses a dangerous precedent or even a cover for partisan attacks.

In the past week alone, a new book resurfaced previously reported concerns among the president’s own advisers about his fitness for office, the question of his mental state came up at two White House briefings and the secretary of state was asked if Mr. Trump was mentally fit. After the president boasted that his “nuclear button” was bigger than Kim Jong-un’s in North Korea, Richard W. Painter, a former adviser to President George W. Bush, described the claim as proof that Mr. Trump is “psychologically unfit” and should have his powers transferred to Vice President Mike Pence under the Constitution’s 25th Amendment.

Mr. Trump’s self-absorption, impulsiveness, lack of empathy, obsessive focus on slights, tenuous grasp of facts and penchant for sometimes far-fetched conspiracy theories have generated endless op-ed columns, magazine articles, books, professional panel discussions and cable television speculation.

“The level of concern by the public is now enormous,” said Bandy X. Lee, a forensic psychiatrist at Yale School of Medicine and editor of “The Dangerous Case of Donald Trump: 27 Psychiatrists and Mental Health Experts Assess a President,” a book released last fall. “They’re telling us to speak more loudly and clearly and not to stop until something is done because they are terrified.”