When The Washington Post and ABC asked a similar question in December, they got almost the opposite result. A slim majority of 51 percent said the deaths up until then were isolated incidents, while just 43 percent said they were part of a pattern. The overall 12-point drop is driven by a shift among white Americans, from 60 percent to 45 percent seeing the incidents as isolated. PRRI finds that three-quarters of blacks see a pattern.

What's changed since December? First, the more recent cases perhaps leave less gray area for the casual observer. Grand juries declined to indict officers in the Brown and Garner cases, but the Scott and Gray cases seem less ambiguous. Video of Scott's shooting, as he ran away from an officer, elicited widespread horror. While much is still unknown about Gray's death, the fact that he apparently sustained fatal injuries in police custody has struck a chord.

Another factor: social and geographic segregation. As Robert P. Jones noted here in August 2014, most white Americans have few close friends who are black. African Americans have been observing how police interact with black Americans their entire lives, but many white Americans have less experience with the issue. If the intense coverage since Garner's death has been one's main exposure to the issue, it would make sense for cases to look more like a pattern as examples pile up.

Still, there are divisions. PRRI finds that 61 percent of Democrats see the killings as part of a pattern, while 65 percent of Republicans say they're isolated. Seventy percent of minority Protestants and 61 percent of religiously unaffiliated Americans see a pattern.

Almost six in 10 white evangelical Protestants think the killings are isolated cases. That's not just a matter of overlap with white conservatives; Jones, who is PRRI's CEO, told me that even after controlling for conservatism or Republican affiliation, white evangelicals stuck out. As my colleague Emma Green noted in a deep dive last month, the Southern Baptist Convention is in the midst of a push on racial reconciliation, but it has a steep hill to climb. Not only was the denomination founded as a pro-slavery splinter group, but its focus on individual responsibility for salvation and sin may make Southern Baptists less likely to perceive systemic issues.

The general disagreement over whether killings of black men by police are isolated or connected might seem irrelevant in the context of past debates about criminal justice: If blacks and whites are divided on everything, this would just be another case. But this moment is different. The media attention to killings has created momentum for criminal-justice reform among both conservatives and liberals—but the pattern question could affect how the debate over it proceeds.

Last week, Conor Friedersdorf criticized conservatives, and particularly movement conservatives, for failing to speak out more about police abuses. The PRRI poll shows that it is true that a strong majority of rank-and-file conservatives see these killings as isolated incidents. But the conversation at the level of writers and thinkers is interestingly different—there are notable conservatives who are concerned about the deaths.