There's a school of political thought that holds you should stay out of the fray when an opponent is wounding himself. That's not Hillary Clinton's way.

The Democratic presidential frontrunner has come out with a devastating new ad that plays on House Majority Leader Kevin McCarthy's now-famous Benghazi gaffe. In an interview on Fox News last week, McCarthy tied Clinton's sagging poll numbers to the special committee House Republicans created to investigate 2012 terrorist attacks in Libya.

It was a stunning acknowledgment of the political nature of the committee's work, and Clinton allies believe it will take the sting out of the investigation. Moreover, it couldn't have come at a better time — or on a better issue — for her. That's because she's locked in a primary against Bernie Sanders, and possibly Vice President Joe Biden, and some Democrats have been concerned about her handling of the email scandal at the center of the committee's work. Now Democrats have a vivid reminder of just how much Republicans hate Clinton, which could help rally them to her defense.

That explains why Clinton is putting an ad on cable television to make sure voters don't forget what the GOP floor leader said. The ad contrasts McCarthy bragging about the committee's role in hindering her campaign with Clinton's push on substantive issues.

"Everybody thought Hillary Clinton was unbeatable, right?" McCarthy says at the beginning of the 30-second spot, which will begin airing Tuesday. "But we put together a Benghazi special committee. What are her numbers today?"

Then a narrator spins the moment to Clinton's favor.

"The Republicans have spent millions attacking Hillary because she's fighting for everything they oppose. From affordable health care to equal pay, she'll never stop fighting for you, and Republican know it," the narrator says over triumphant images of Clinton.

And then the kicker: "I'm Hillary Clinton, and I approve this message."

Several House Democrats, including Minority Leader Nancy Pelosi, have called for House Republicans to dissolve the Benghazi committee in the wake of McCarthy's remarks. But as the ad demonstrates, Clinton thinks she'll now have the upper hand at her October 22 hearing.