Hillary Clinton is testing out a strategy that has backfired on Republican presidential candidates: trying to take the high road in the face of a personal attack from Donald Trump.

Campaigning in Iowa on Monday, Clinton called Trump’s anti-Muslim comments “not only dangerous, but shameful,” and doubled down on her charge during the Democratic debate last Saturday that he has become ISIL’s biggest recruitment tool. But the former secretary of state made no mention of the headline of the day — Trump’s lewd personal attack that she lost in the 2008 primary to Barack Obama because “she got schlonged.”

Turning the other cheek when insulted by the bullying front-runner has backfired in the past for candidates like former Florida Gov. Jeb Bush, who refrained from hitting back against Trump until long after the withering insult that Bush was a “low-energy” candidate was baked into his image.

But Clinton’s campaign refused to take the bait on Tuesday. Using Trump’s favorite communication tool, Twitter, Clinton communications director Jennifer Palmieri explained Tuesday morning there would be no engagement on Trump’s "schlong" comment, made at a rally Monday night in Grand Rapids, Michigan.

“We are not responding to Trump,” she wrote, “but everyone who understands the humiliation this degrading language inflicts on all women should. #imwithher.”

Meanwhile, the pro-Clinton rapid response group Correct the Record, which coordinates with the campaign and defends Clinton against attacks, was uncharacteristically silent in the face of the sexist broadside. 

The Clinton strategy appears to be to double down on attacking Trump over policy, including a vigorous defense of Clinton’s claim that Trump is providing recruiting material for the Islamic State, also known as ISIL or ISIS, with his bombastic denunciations of Muslims. Thus, Clinton will show that she’s unafraid of taking on Trump, while refusing to engage in a mutually demeaning exchange of insults. 

Clinton supporters argue that, unlike their candidate, Republican contenders were timid about starting a war with Trump over policy differences on immigration and other issues that could hurt them with the primary electorate fired up by Trump’s incendiary rhetoric. But Clinton is hoping those contrasts will energize her base without engaging in a degrading war of words with the bombastic billionaire.

Handling Trump’s attacks without feeding into his playbook is a problem that has roiled the Republican field — and Monday's sexist comment was a sign of how the race could devolve if a general election battle pits Clinton against Trump.

In the primary, Trump has used personal insults to make candidates seem weak or unattractive or unfit for office, and their failure to respond seems only to confirm the truth of Trump’s attack.