One major difference between politics today and politics from around the turn of the century to about the 1980s was some of the major conflicts were not between parties but within parties. During the Progressive Era, there were progressives and conservatives within both parties, TR and Wilson were not that different. The same is true during the early years of the Cold War. The fight against the communists was not between the two parties but within each. Truman wanted to fight communists, but other Democrats wanted to continue our relationship with Russia after WWII. Same with Republicans, there were those who agreed with Truman and wanted to contain communism everywhere and others like Robert Taft, who wanted to pull all our forces back to America and build a American fortress and practice isolationism. Today with every issue if one party is for it the others has to be against it, but it was not always that way.
Historically Speaking 