**FILE** An Aug. 28, 1968 file photo shows a demonstrator with his hands on his head is led by Chicago Police down Michigan Ave. during a confrontation with police and National Guardsmen who battled demonstrators near the Conrad Hilton Hotel, headquarters for the Democratic National Convention. It's been 40 years since scenes such as this played out, as Democrats head to Denver Aug. 25-28 to nominate a presidential candidate. While the 2008 convention won't look anything like that one, much of what will happen _ and won't happen _ is a direct result of what unfolded in Chicago when, as the protesters shouted, "The whole world is watching." That includes the nomination of Barack Obama, just four years removed from being an obscure Illinois state senator. (AP Photo/File)