Why, given a strong presumption of success, do some presidential nominations fail? Of 1,464 important nominations from 1965 to 1994, less than 5% failed. Ninety-four percent of failures were rejected or withdrawn before reaching the floor, suggesting that opponents are most effective during prefloor stages. We propose a theoretical framework based on the notion that policy entrepreneurs pursue their goals within the context of a presumption of success. Logit analysis tends to support the theory that entrepreneurs can alter the presumption of success and defeat a nomination if they (1) identify negative information about a nominee to provide a rationale for changing the presumption and (2) expand the conflict through committee hearings and the media. Presidential resourceshigh public approval and efforts to signal that the nomination is a high priorityincrease the chances of confirmation. Contrary to previous research, divided government has no independent effect on the fate of nominations.