This editorial has been updated.

"FEAR-MONGERING." That is the title of an ad being aired by Virginia Democrat Ralph Northam that takes aim at ads by Ed Gillespie, his Republican opponent for governor, trying to tie Mr. Northam to MS-13 gang violence and to a child pornographer. Mr. Northam is correct in his assessment of the poisonous ads and correct that it is "despicable" to imply he would tolerate anyone hurting a child. But just as despicable is an anti-Gillespie ad created by an independent group that supports Mr. Northam. It behooves Mr. Northam, while he is offering criticism, to make clear that even though the anti-Gillespie spot was not a product of his campaign, his campaign wants no part of it.

The minute-long spot from the Latino Victory Fund depicted a pickup truck being driven by a sinister-looking white man, flying a Confederate flag and sporting a Gillespie bumper sticker as it chased down a group of terrified brown-skinned children. Titled "American Nightmare," the ad ended with the children waking up from a nightmare and adults watching television footage of August's torch-bearing white-nationalist march in Charlottesville. "Is this what Donald Trump and Ed Gillespie mean by the 'American Dream?' " asked the narrator.

There is no question that if this were a race to the bottom, Mr. Gillespie would be the winner, having spent millions of dollars on ads that use specious claims and appeals to race and ethnicity to scare and divide. That he has doubled down in recent days with deceptive ads trying to paint Mr. Northam as an enabler of child predators underscores the lack of character that has marked his campaign. It is one reason we endorsed Mr. Northam.

But just because Mr. Gillespie has resorted to gutter tactics doesn't give others leave to do the same. The Latino Victory Fund ad was vile. Among other faults, it glossed over the fact that Mr. Gillespie condemned the white-supremacist violence in Charlottesville far more directly than did President Trump.

"Ralph Northam would not have run this ad and believes Virginians deserve civility, not escalation," a spokesman for Mr. Northam emailed us. That was before the Latino Victory Fund announced Tuesday night that it was pulling the ad, issuing a statement that cited "recent events." Maybe that was a reference to Tuesday night's truck attack in Manhattan. It is sad that it took such a tragedy for the group to realize how out of bounds its ad was. It's also sad that someone who promises to be a governor for all Virginians didn't call them out right away.