Since 1980, more than 175 scholarly articles, chapters, or books have been published about the post-reform presidential nomination system. Numer ous authors investigate primary rules, media coverage, candidates, voters, or momentum. Less well covered are the subjects of interest groups, win nowing of candidates, campaign contributors, and connections to other phases of the presidency Research on presidential nominations has to con tend with an ever-changing environment as rules change, candidates exit the contests, and the primary season progresses from February through June. This environmental complexity adds to the challenge of investigating the first phase of the presidential selection process. Coupling this environ mental complexity with a lack of consensus among scholars on measure ment, model building, and theory leads to contradictory findings in a number of areas. Nevertheless, much has been learned about the patterns of presidential nominations.