If President Donald Trump hadn’t bragged at a campaign rally in Alabama that if he were an NFL owner, he would fire any “son of a bitch” who knelt during the national anthem, would Colin Kaepernick be a face of Nike’s Just Do It campaign? Would a black-and-white image of Mr. Kaepernick’s face with the words, “Believe in something even if it means sacrificing everything” be ricocheting around the internet today if an NFL team, any NFL team, would have so much as signed him as a backup quarterback? Would players still be following his example to kneel or even raise their fists during the national anthem if his efforts to bring attention to racial injustice had been taken at face value and not as an affront to the flag, military and country?

All those posting images of burned or defaced Nikes since word spread of Mr. Kaepernick’s new Nike campaign over the weekend should consider this: It is they who transformed him from a quarterback whose career had been middling since taking his team to (and losing in) the Super Bowl into an icon, someone whose cultural power far transcends sport.

Nike isn’t so much thrusting him back into the spotlight as it is recognizing that he’s already there — and capable of selling shoes. Mr. Kaepernick’s jersey leaped to the top of sales lists after the anthem protests started in 2016 and stayed in the top 50 last year despite the fact that he wasn’t on an NFL roster. Nike’s stock may have dipped slightly in early trading after the announcement, but here’s betting that the sports equipment giant did some marketing research before signing what is reportedly a multi-year, multi-million-dollar deal with an athlete who is suing his former league and may never play again. Whatever buzz Under Armour may have gotten from its unconventional and statement-making ad choices in the past (like the exceptional Misty Copeland campaign of four years ago) pales next to this.

Why does Mr. Kaepernick still resonate? Part of it is certainly the fact that he has, as the ad suggests, genuinely sacrificed a great deal in the name of principle. That’s always an intriguing narrative, and particularly so in the Age of Trump. Last week’s tributes to the late Sen. John McCain traded heavily on that notion. But there’s also the simple fact that Mr. Kaepernick’s message about protesting racial injustice has only become more relevant since its origins at the height of the Black Lives Matter movement. Then, the nation’s first African American president was (however imperfectly) seeking to achieve the kind of racial reconciliation many assumed had already arrived with his election. Now, we have a president who posits moral equivalence between white supremacists and those who protest them, emboldening those who would exacerbate and exploit racial division.

News about the Kaepernick ad came on the same weekend that the Tallahassee Democrat reported on robocalls linked to a white supremacist group in which a man speaking in a racist exaggeration of a minstrel performer’s dialect pretends to be the Democratic nominee for Florida governor, Andrew Gillium, who is African American. The recording, which includes a backdrop of jungle sounds, makes reference to his Republican opponent’s statement a few days before that Florida voters shouldn’t “monkey this up” by voting for Mr. Gillium.

Colin Kaepernick still matters because his message still does. NFL owners couldn’t make him go away by keeping him off a team (whether through outright collusion, as his lawsuit alleges, or a more informal groupthink), and they couldn’t stop the protests that stemmed from his activism through ham-fisted attempts at compromise with the players. President Trump raised the stakes too high for that. Nike, who has had Mr. Kaepernick under contract since 2011, is doing nothing more than taking advantage of the opportunity the president and his allies so cynically created.

— The Baltimore Sun, Sept. 4