Word is that Mr. Trump isn’t doing a whole lot of debate prep. But his team ought to have at least readied him for what should be the easy response to all the nasty attacks. Mrs. Clinton’s own past is so malodorous, so rife with crooked deals and lies, that Mr. Trump shouldn’t have to do much more than calmly question her credibility and then move on to better subjects.

Mr. Trump’s impulse no doubt will be to take it to her, to hit back, to dwell on Mrs. Clinton’s malfeasance. No doubt a few tough reminders to the audience of her ethical failings are necessary. But everyone already knows Mr. Trump is a scrapper. What he needs to show now is that he has his own optimistic and considered plans for change in America. This is one of his openings. In that same New York Times/CBS poll, 48% of voters felt Mr. Trump could bring about “real change.” Only 36% said that of Mrs. Clinton.

By being positive, Mr. Trump would draw a stark contrast. Mrs. Clinton these days looks perpetually angry and seems to have only one volume setting: yell. The press keeps noting that she is a seasoned debater, but then again she has mostly debated fellow Democrats and been questioned by sympathetic press. Her style is fairly predictable.