Though it lags behind the misogyny and the racism and total ignorance of domestic and foreign policy, Trump’s extremely short attention span is one of the (many) unpresidential qualities that has dogged him for much of the general election campaign. The Art of the Deal ghostwriter Tony Schwartz told The New Yorker’s Jane Mayer that Trump’s attention span is shorter than his fingers: “After sitting for only a few minutes in his suit and tie, Trump became impatient and irritable. He looked fidgety, Schwartz recalls, ‘like a kindergartner who can’t sit still in a classroom. ... If he had to be briefed on a crisis in the Situation Room, it’s impossible to imagine him paying attention over a long period of time.’”

Trump’s inability to stay focused was on full display on Monday night:

Trump brings up Russia, then China, then a 400 lb. hacker, accuses Clinton of railroading Bernie Sanders, then discusses how good his 10-year-old son is at computers, before concluding that we have to do cyber better.

Trump’s lack of preparation is being blamed for his poor performance—as is, it seems, the fallout from Roger Ailes’s dismissal from Fox News. Here’s The New York Times on Trump’s debate prep:

Mr. Trump found it hard to focus during those meetings, according to multiple people briefed on the process who requested anonymity to discuss internal deliberations. That left Mr. Ailes, who at the time was deeply distracted by his removal from Fox and the news media reports surrounding it, discussing his own problems as well as recounting political war stories, according to two people present for the sessions.

Lack of preparation is a common excuse for poor debate performances—it took the blame when President Obama stuttered out of the gate against Mitt Romney in 2012. The difference, however, is that Obama’s fitness for the office wasn’t a major question in 2012. Trump’s total lack of debate preparedness suggests that he’d be similarly lost in the Oval Office.