Less common patterns are a convention choice among major candidates, or the surprise selection of a relatively unknown dark horse after many ballots. In vice presidential selections, there has not even been a contest in more than two thirds of the modern nominations. The choice of a running mate is usually prearranged in consultations between the new presidential candidate and other party leaders. An exception came in 1956, when the Democratic nominee, Adlai Stevenson, refused to name a preference, and permitted the convention to select Sen. Estes Kefauver after a spirited two-ballot contest. The relatively limited choice available to conventions since World War II is due to the greater influence of preconvention factors.
Primary elections bind many delegates.
Early campaigning exposes the presidential aspirants to the party long before the formal decision. Television coverage also publicizes the candidates more fully, while it makes it more difficult for party leaders to negotiate privately. Convention decisions are also strongly affected by public opinion polls, which indicate the popular favorites. Because delegates are eager to win the election, they usually select the person leading in the polls. The increasing power of the president and the importance of national issues also makes it difficult for conventions to choose inexperienced candidates unfamiliar with those issues.