Half of Americans doubt President Donald Trump is mentally fit to lead the nation, according to a new

.

Forty-seven percent of respondents claimed to believe Trump "not mentally stable," versus a slight majority of 48 percent attesting to the opposite.

A periodically reoccurring topic of discussion since Trump began his 2016 presidential campaign, the question saw renewed urgency after the release of journalist Michael Wolff's book "Fire and Fury" earlier in the month.

Various details addressed in the book -- Trump's short attention span, flimsy grasp on foreign and domestic policy implications and the broad questioning of his fitness for office by key players in his administration -- spurred the discussion.

On Jan. 6, the day after the book's official release, Trump took to Twitter to address the matter.

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..... — Donald J. Trump (@realDonaldTrump) January 6, 2018

....Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart. Crooked Hillary Clinton also played these cards very hard and, as everyone knows, went down in flames. I went from VERY successful businessman, to top T.V. Star..... — Donald J. Trump (@realDonaldTrump) January 6, 2018

....to President of the United States (on my first try). I think that would qualify as not smart, but genius....and a very stable genius at that! — Donald J. Trump (@realDonaldTrump) January 6, 2018

Meanwhile, the president's latest approval numbers, captured in the same poll, were 38 percent thumbs up, 58 percent down.

The poll sample size was 1,005 adults and the results have a margin of error of 3.5 percent.