As much as our country has become divided and polarized in recent years, marketers could pretty much count on sports offering a respite from the turmoil and strife. Signing athletes as endorsers was one of the mainstays in the marketing playbook, and as long as they didn't embarrass themselves on the field -- or off the field, with inappropriate personal behavior -- consumers invariably responded positively. Stars such as Tom Brady, Kevin Durant, Bryce Harper, LeBron James, Peyton and Eli Manning, John McEnroe and Michael Phelps have parlayed their popularity into billions of dollars’ worth of endorsement and sponsorship deals. Now, like so many other things we've taken for granted, that's starting to change. No longer are sports and athletes above the fray, or sealed off in a fun-and-games world of their own.