Selection of the two major party presidential candidates has been determined by state by state gauntlet called the Presidential Primary Campaign since 1972, when the McGovern-Fraser Reforms were adopted. Candidates are winnowed in a process of attrition that tests their acceptability to the party faithful in different and less than representative states rather than to the general electorate in the country as a whole. Republican presidential primaries more efficiently winnow candidates than do Democratic presidential primaries.
- Wayne P. Steger, John Hickman and Ken Yohn. "Candidate Competition and Attrition in Presidential Primaries, 1912-2000." AMERICAN POLITICS RESEARCH, Vol. 30 No. 5, September 2002. text