Apophasis, as students of rhetoric know, is the speechmaker’s trick of raising a nasty subject by saying you’re not going to talk about it. But it isn’t easy to pull off. It requires a light touch; once you raise the taboo subject, you can’t go back to it — a subtlety lost on Donald Trump, it seems.

At the end of his debate with Hillary Clinton, Trump said he considered mentioning Bill Clinton’s history of sexual misconduct, but decided that would be wrong. “It’s inappropriate. It’s not nice,” he said, noting that Clinton’s daughter was in the audience.

Allies praised his statesmanship. “He was a gentleman,” former House Speaker Newt Gingrich said. “That took a lot of courage,” his son Eric Trump said.

His restraint didn’t last long, though. Over the next several days, Trump and his campaign continued raising the subject he didn’t mention.

“I was talking about the affairs — the many affairs that Bill Clinton had,” Trump said the next morning. (A telling slip; he meant the affairs he wasn’t talking about.)

“The American people have had it with years and decades of Clinton corruption and scandals … and impeachment for lying. Remember that, impeach,” he said at a New Hampshire rally. “The Clintons are the sordid past; we will be the very bright and clean future.”

His campaign staff even issued talking points to supporters, offering helpful tips on how to talk about Clinton scandals.

“Are you blaming Hillary for Bill’s infidelities?” the tip sheet offered. “No, however she’s been an active participant in trying to destroy the women who [have] come forward with a claim.”

Actually, the evidence that Clinton was an “active participant” in attacking her husband’s accusers is scanty, beyond the fact that she stood by her husband and said she didn’t believe their charges. But that didn’t stop Trump’s surrogates.

“Look at what she has done: Gennifer Flowers, Paula Jones, Monica Lewinsky,” Rep. Marsha Blackburn, a Tennessee Republican, told MSNBC. “My goodness.”

GOP strategists have a term for dredging up Bill’s scandals: “the nuclear option.” They’ve waited all campaign long to see whether Trump would pull the trigger. Now, despite his short-lived attempt at apophasis, he has.

The danger is obvious: The fallout could hurt him as much or more than the intended target.

“It’s like a nuclear hand grenade,” Republican pollster David Winston told me. “As Trump blows everything up, does he blow himself up as well — or does he only get damaged around the edges?”

“It’s totally the wrong direction to go,” Gingrich, who led the drive to impeach Bill Clinton in 1998, told the Washington Post. “He should not let them bait him into a swamp where they can revel in the mud.”

Yet that’s where Trump went.

He also made a second, even briefer attempt at apophasis when it came to Alicia Machado, the former Miss Universe who accused him of bullying her when she gained weight.

“A lot of things are coming out about her,” he told Bill O’Reilly on Fox News on Wednesday. “I’m not going to say anything.”

And then he did, in a flurry of tweets at 5 a.m. Friday, including one that urged voters to “check out [a] sex tape” that allegedly includes Machado.

As he flails, Trump is using precious campaign time to talk about the wrong subjects: sex scandals and sex tapes rather than his promises to fix the economy. And these tangents seem unlikely to improve his standing among women voters, most of whom already consider him unpalatable. He might actually end up giving his rival a sympathy boost.

In 1998, during the impeachment proceedings against Bill Clinton, Hillary Clinton’s popularity soared. Earlier this year, a Democratic polling firm asked voters whether Hillary Clinton should be held accountable for her husband’s misconduct, and a large majority — including 56 percent of Republicans — said no.

That said, Trump’s dive into the swamp may also create problems for the Democratic candidate, who says she wants to spend the final weeks of the campaign talking about positive themes — mainly, her proposals for creating jobs and making the economy fairer. When Trump’s charges dominate the news and Clinton responds to the targets he provides, few other messages are likely to break through.

On Friday, for example, Clinton gave a long speech outlining her proposal for a national service program — but the headlines, predictably, were about her description of Trump’s “strongman approach.”

Ultimately it’s the voters, on all sides, who stand to lose the most. We need to hear about job creation and foreign policy. Instead we’re arguing about Gennifer Flowers and Miss Universe. In a presidential campaign.

— Doyle McManus is a columnist for the Los Angeles Times.