Infographic of shifting US political ideologies OCT 22 2012
It was not my intent to be so politically oriented this morning but here we are. This is a chart that tracks the ideologies of the Democratic and Republican members of Congress from 1789 to 2010. As you can see, the shift away from the center by the Republicans since 1975 is unprecedented, perhaps matched only by the shift toward the center by the Democrats beginning in 1921 and ending in 1945.
This reminds me of a timeline created circa 1880 for a book called Conspectus of the History of Political Parties and the Federal Government: