Paul Krugman calls Trump 'obviously mentally ill the moment he took office' in bizarre tweet

Paul Krugman, the Nobel Prize winning economist and liberal New York Times columnist, questioned the mental health of President Donald Trump in a tweet Tuesday morning.

"An American first: a president who was obviously mentally ill the moment he took office," Krugman tweeted.

"Thanks, Comey," he added, referring to FBI Director James Comey.

Krugman has criticized Trump repeatedly since his election - questioning Trump's business conflicts of interest, his Cabinet nominees, the involvement of Russia in his election, and more. But this is the first time Krugman called into question the mental fitness of the president.

Trump received a clean bill of health from his doctor prior to the election.

Krugman has also been critical of Comey, whose letter to Congress regarding Hillary Clinton's email investigation, he has argued, swung the election in Trump's favor.

Krugman highlighted part of a Washington Post article about Trump's attitude following the election, tweeting, "Read it and shudder."

In subsequent tweets, Krugman also said that despite Trump's best efforts, the growing difference between increasing US interest rates due to rate hikes from the Federal Reserve and the interest rates throughout the rest of the world will increase the strength of the US dollar. In turn, a strong dollar will be harmful to US manufacturing, offsetting any pro-manufacturing policies from Trump, Krugman said.

Here are the tweets: