what makes a politician ?

I have been watching the primaries in US . Specially the democratic ones. It was a pretty good race. Sometimes the squabbling, between the two made me wonder, are politicians different at different places in the world? Can Lalu or Chandra babu, win primaries in US. Can Clinton or Obama win elections in India? Is there a fundamental difference between them? If a good and determined man ( a non politician) ever takes the highest office, can he change the course of the nation? So in shortwhat makes a politician?