Just picture this...
In November 2008, Senator John McCain wins the U.S. Presidential election.
On January, 2009, President McCain announces in his inauguration speech that he is leaving the Republican party and joining the Libertarians.
Think of the circus!
Or... if that doesn't sound like any fun to watch, imagine for just a second the presidential election between Hillary Clinton and Condoleeza Rice.

Yeah... I'm bored.