美国的政党历史上发生过多次政策转移。现在的政党阵营形成于60年代之后的洗牌。早期的党派名称不能说明问题。见来源：

Sources:

http://www.huffingtonpost.com/rich-rubino/democratic-and-republican-ideologies_b_3432210.html

“The Democratic and Republican Parties have undergone a long transition from their founding ideological principles. The Democrats started out as the conservative party but are now the liberal party, and the Republicans were once the liberal party but are now the conservative party.”

http://us-presidents.insidegov.com/stories/3613/republicans-democrats-switch-platform

http://www.stat.columbia.edu/~gelman/research/published/reversal2.pdf