U.S. President Donald Trump on Wednesday again criticized Nike for its advertising campaign with Colin Kaepernick, the NFL quarterback who sparked a national controversy by kneeling during the national anthem.

Trump tweeted, without offering evidence: "Just like the NFL, whose ratings have gone WAY DOWN, Nike is getting absolutely killed with anger and boycotts. I wonder if they had any idea that it would be this way? As far as the NFL is concerned, I just find it hard to watch, and always will, until they stand for the FLAG!"

He also continued to blast National Football League players for their protests over racial and social injustice.

It is the second time that the president has weighed in on the campaign, having called it “a terrible decision” in an interview with the Daily Caller published on Tuesday.

Representatives for Nike could not be immediately reached for comment on Trump’s tweet. Shares of the company were up less than one percent in midmorning trade on Wednesday; the stock had dropped nearly 4 percent at one point on Tuesday.

The footwear and apparel maker’s campaign this week further stoked a national debate over social justice that Kaepernick and other NFL players sparked with their protests aimed at addressing police brutality against minorities, racial injustice, and reforming the criminal justice system.

Trump has embraced the issue as a political cause, frequently criticizing players for taking a knee at games and questioning their patriotism. Critics have defended their protests as a fundamental American right to free speech.

Marketing experts predicted that the brand recognition sparked by the ads would be successful in the long run, despite current calls for boycotts on social media.

NFL players and the league are continuing to negotiate over the issue of protests.