For Trump, that's critically important.

Americans broadly dislike Donald Trump and Hillary Clinton, but that doesn't mean they view the two candidates the same way. Clinton's generally viewed a bit more positively, and both are seen as about equally distrustful. But on basically every other metric, including the critical question of whether the candidates are qualified for the job, Trump fares much worse.

Our polls with ABC News have repeatedly shown that about 60 percent of Americans don't view Trump as qualified to be president, while the same number see Clinton as ready for the job.

That's not prohibitive, interestingly; 4 percent of likely voters who see Trump as unqualified still plan on supporting his candidacy, according to our most recent survey. But overwhelmingly, people who see Trump as unqualified plan on voting for his opponent.

Why do people view him as unqualified? Last month, Quinnipiac University asked people that precise question. The most common response? His temperament.

In our most recent poll, those who viewed Trump's temperament negatively preferred Clinton by a 70-point margin. Among independents, there's a wide gender gap. Half of independent men say Trump has the personality and temperament to serve as president. Only a little more than a third of independent women say the same. Among Republicans, there's no gender gap -- but among white women with college degrees, a critical voting bloc that support Mitt Romney four years ago, only 29 percent of likely voters viewing Trump's temperament as acceptable. That group of likely voters now backs Clinton by 25 points.

Maybe this debate won't matter. "Temperament" is a vague term, subject to interpretation. Perhaps Trump's rally persona is the one people prefer. Worked for him in the primary. By the end of the debate, he'd mellowed. Maybe that was enough.