Of course, it doesn’t help Mr. Trump if the media continue to focus on Ms. Machado and the GOP nominee has to defend himself from her charges. Rehashing his past dealings with Ms. Machado only distracts from Mr. Trump’s overarching theme of putting America back on track. That’s clearly the Clintons’ hope, since his central message — economic growth, national security and safe communities — clearly resonates with many voters. And while Mr. Trump is still the underdog, polls say he remains competitive despite a hostile press, his mediocre debate performance and his opponent’s multimillion-dollar attack ad buys.

The Clintons are past masters at putting their opponents on the defensive, but enlisting Ms. Machado for their cause could open up a can of worms for Mrs. Clinton. As he himself noted Monday night, Mr. Trump has restrained himself when it comes to talking about Bill Clinton’s treatment of women in the past.

Some in the GOP are advising Mr. Trump not to go after Mrs. Clinton on her husband’s infidelities and her own role in covering up his alleged sexual predations toward women. The Clinton campaign has stated that she will be ready to respond to Mr. Trump if he brings up her husband.

But it’s not so simple: Questions remain on why Mrs. Clinton called women who were involved with her husband “bimbos” and how her husband and his aides focused on destroying his accusers. Mrs. Clinton stands accused of protecting her husband’s political career — and her own — by belittling, bullying and smearing women like Paula Jones, Gennifer Flowers and Monica Lewinsky. Ms. Lewinsky even was moved to start an anti-bullying foundation after her ordeal at the hands of the Clinton machine.