A billboard in San Francisco shows a new Nike ad featuring former San Francisco 49ers quarterback Colin Kaepernick. (Eric Risberg/AP)

Believe in something. Even if it means sacrificing everything.

As an exhortation, it’s banal, the sort of thing a kindly granddad imparts toward the end of a Hallmark Channel movie. As ad copy for Nike, superimposed on a photo of former San Francisco 49ers quarterback Colin Kaepernick’s face, it’s apparently more electric.

On Wednesday, Nike unveiled the advertising campaign featuring Kaepernick, who in 2016 catalyzed some National Football League players’ refusal to stand for the national anthem as a protest of police brutality toward Americans of color.

Social-media political performance artists leaped into action. Nike shoes were burned. Swooshes were snipped from socks. America’s tweeter in chief predicted doom for the brand.

It seemed as if we were in for yet another round of national Choose Sides.

That’s not quite how it’s working out.

Shortly after Nike’s announcement, the consumer-research firm Morning Consult released a survey showing that Nike had indeed, as President Trump predicted, taken a reputation hit from its overtly political campaign. Interviews with 8,000 Americans showed a nearly 50 percent decline in Nike’s favorability after announcing the Kaepernick ad campaign. Consumer interest in buying Nike products dropped by 10 percentage points.

Which you might expect. A polarizing political endorsement is going to cost a company with customers on the other side of the issue, though it may still pay off in terms of greater loyalty from people who agree. But surprisingly, the endorsement wasn’t really all that polarizing. Yes, the percentage of Republicans saying they were likely to buy Nike shoes fell from 51 percent to 28 percent, but support also dropped among Democrats, albeit only by five percentage points. Blacks and young people, two demographic groups that the Nike campaign presumably was intended to woo, also seem to have been turned off: The number of African Americans interested in buying Nike dropped from 64 percent to 61 percent, and 18- to 21-year-olds reported a decline of nearly 20 percentage points.

The groups no doubt have different reasons for disliking the…