And this is how new parties form. As a party expands to include more and more of the center eventually fissures in the party grow and eventually they split off

And this is how new parties form. As a party expands to include more and more of the center eventually fissures in the party grow and eventually they split off to form a new party (See http://xkcd.com/1127/ http://xkcd.com/1127/ Show the leaning of congress since the start; parties follow a similar constant churning). Do you really think it's been democrats vs republicans since the USA was founded?