Obama, Clinton, McCain, Romney, Paul.....?

How come on just about every question Barack Obama, or Hillary Clinton is the only ones being talked about, not to much talking on John McCain, or Mitt Romney, Ron Paul.. Is this a matter of Support for Obama and Clinton.. Or just Republicans scared that two people that will make a good team will take the white house.. Or just mad cause a women, and black man are running for president. Cause I really dont understand it. Seems Weird to me..