Obama was a rock star in 2008. Def Lepard or Poison, if you will, larger than life, talked in platitudes (Hope and Change ... so vague, but catchy), and filled an entire NFL stadium during thunderstorm season in Denver. Stadium rock for that time in America.
Obama in 2012 has moved to smaller venues, unable to fill the stadiums anymore, while the realistic candidates (I'll call them grunge to Obama's hair band) Romney/Ryan continue to hammer away on the reality of Obama's policies. Grunge never really played to huge crowds, but it was real, and in small clubs, it spoke deeply to those listening. The hair band ideals of hot chicks, men wearing spandex and make-up, and big hair look goofy these days, at the time they were popular. They seemed really cool to people unable to look in a mirror and see how ridiculous they looked at that time.
It's not really Obama's fault that he sucks so bad. It's just that much of his audience has moved on to reality, and the true devotees look out of step with the current social climate.