Donald Trump had one job: To seem level-headed. He failed miserably.

Trump’s temperament has been the biggest issue of this campaign. Voters worry about his ability to maintain control of his emotions. His task was to show voters that his skin isn’t as thin as it has seemed over the last 15 months. That was the incredibly low bar set for him.

Clinton got under Trump’s skin early. He got mad and he stayed mad for the course of nearly 90 minutes. Halfway through the debate, he was raving; by the end of the evening, he had completely lost it. Hit repeatedly by Clinton (and, it should be said, by the often absent moderator Lester Holt) on his lies about supporting the Iraq War, he lost the thread, and started ranting at Holt about how is temperament is actually great, literally disproving the point he was making. He was overly defensive and it showed. Instead of succinctly and clearly answering questions, he rambled and ranted.

But the most amazing point was at the very end of the debate, when Clinton brought up Trump’s repeated sexist comments. Once again, Trump took the bait and went on an extended rant about how those comments were justified—Rosie O’Donnell had it coming! Given the opportunity to give one example of how he was not a sexist, he instead argued that the women deserved the attacks he slung at them. And then he threatened to bring up Bill Clinton’s infidelity and claimed the fact that he didn’t was proof that he wasn’t sexist.

This can’t be overstated. Donald Trump’s temperament has been the defining issue of the last year of this campaign. And yet, on the biggest possible stage—the most important of the last year—Trump repeatedly lost his temper.