Nike Inc. (NKE) shares fell the most in two months Tuesday after the sportswear giant unveiled a new advertizing campaign featuring Colin Kaepernick, a former NFL quarterback who inspired a series of nation-wide protests against police brutality and social injustice but courted controversy by kneeling during the playing of the national anthem.

Nike chose Kaepernick, who is currently suing the National Football League for collusion after he failed to find a spot on any team roster despite leading the San Francisco 49ers to the Super Bowl in 2013, to lead the 30th anniversary of its iconic 'Just Do It' campaign that includes tennis superstar Serena Williams and skateboarder Lacey Baker. Kaepernick's participation was first made public via his official Twitter account late Sunday with the phrase "Believe in something, even if it means sacrificing everything."

"We believe Colin is one of the most inspirational athletes of this generation, who has leveraged the power of sport to help move the world forward," Nike North America vice President Gino Fisanotti told ESPN.

Nike shares were marked 2.5% lower in the opening minutes of trading on Wall Street, the biggest decline since July 3, and changing hands at $80.14 each, a move that still leaves the stock with a year-to-date gain of around 28%.

Believe in something, even if it means sacrificing everything. #JustDoIt pic.twitter.com/SRWkMIDdaO

— Colin Kaepernick (@Kaepernick7) September 3, 2018

While Nike's previous campaigns have defined sports culture in the United States and helped developed the global stardom of athletes such as Tiger Woods, Michael Jordan and Roger Federer while generating billions in revenues for the world's biggest sportswear company, its current effort has courted immediate controversy and could lead to customer backlash in its biggest market, where it is already losing ground to its main global rival Adidas AG  (ADDYY) .

Twitter hashtags such as #BoycottNike and #JustBurnit have gained significant traction in the hours following Kaepernick's Tweet, and very likely to attract the attention of President Donald Trump, who has used his own account on several occasions to attack the NFL, its commissioner Roger Goodell, and various American football players for kneeling during the playing of the national anthem.

The NFL players are at it again - taking a knee when they should be standing proudly for the National Anthem. Numerous players, from different teams, wanted to show their "outrage" at something that most of them are unable to define. They make a fortune doing what they love......

— Donald J. Trump (@realDonaldTrump) August 10, 2018

Kaepernick began kneeling during the anthem in early 2016, and although his actions were not immediately picked up by the local and national media, it soon spread across the league -- and into other professional sports -- as players joined the 30-year old quarterback's silent protest.

Since then, the movement has proven to be both incredibly divisive and significantly costly to the NFL, which has seen a steady decline in television ratings since the first protests and ignited a battle between league officials and the player's union, which has continually supported Kaepernick's actions.

The league ultimately strengthened its position on anthem protests earlier this year and insisted that players stand at attention during the playing of the anthem, but also allowed for the option of staying in the locker room until the completion of the 'Star Spangled Banner'. However, several players have continued to kneel during pre-seasons games this year.

Kapernick, however, has been unable to land a spot in the NFL since becoming a free agent in 2017 and has accused the league of colluding against him on the basis of his political opinions. His case against the league was given a major boost last week, in fact, when he was approval for a full hearing in the ongoing dispute, a move that will allow his legal team to depose NFL officials such as Goodell and team owners such as Jerry Jones of the Dallas Cowboys.

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