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Nike has grown in popularity among millennial investors after releasing its controversial Colin Kaepernick ad.

A total of 15,191 investors added Nike to their portfolios on Robinhood this week, up 45% from last week.

President Donald Trump tweeted Wednesday criticizing Nike's polarizing ad.

The company is trying to reach a younger demographic, an analyst said.

Watch Nike trade in real-time here.

Nike's controversial ad featuring Colin Kaepernick has paid off, at least among millennial investors, according to data from Robinhood, a no-fee brokerage popular among younger traders.

The sneaker maker tapped several athletes including Kaepernick, the football quarterback who protested racial injustice by kneeling during the national anthem, as the faces of a campaign marking the 30th anniversary of its "Just Do It" slogan.

Nike shares are down 2% this week, following the campaign reveal on Monday. Meanwhile on Robinhood, a total of 15,191 investors added Nike to their portfolios this week, up 45% from last week, according to Business Insider's tracking of the data.

"Investors on Robinhood are buying Nike stock 300% more than they are selling, compared to 12% last week," Sahill Poddar, the app's data scientist, told Business Insider on Tuesday. "Investors in Oregon, where Nike is headquartered, are buying the stock 850% more than they are selling."

Nike is the 37th most popular stock on the brokerage, up from 57th last week.

The issue of players kneeling during the national anthem could once again take center stage as the NFL season kicks off on Thursday. It drew the ire of President Donald Trump, who tweeted Wednesday about Nike's ad featuring Kaepernick.

"Nike is getting absolutely killed with anger and boycotts," Trump tweeted. "I wonder if they had any idea that it would be this way?"

According to Oppenheimer analyst Brian Nagel, the sneaker giant is taking some short-term pain for long-term gain. Nagel said that the company is trying "to make some noise" in the industry via its athletes and their stories, regardless of any political leanings, according to MarketWatch.

Shares of Nike are up 29% since the start of this year.

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