Merican Political Culture between 2004 and 2012

What changed, if anything, in the American political culture between 2004 and 2012? This was a period that saw the reelection of two very different presidents, George W. Bush and Barack Obama. Be sure not just to describe the issues that were important in the 2004, 2008 and 2012 elections, but analyze whether or not there were differences in the way that American people related to them.