"But the G.O.P.’s long transformation into the party of the unreasonable right, a haven for racists and reactionaries, seems likely to accelerate as a result of the impending defeat."
"The Republican Rump", Paul Krugman, New York Times, 2008-11-03
Krugman doesn't predict the demise of the Republican Party, but he thinks moderate Republicans will have to confront that their party has become the party of intolerance.
See also "Are we getting closer to a viable third party?"