‘Big Mo’ has just switched uniforms.

—Dandy Don Meredith, football commentator

According to a staple item of conventional wisdom about the politics of presidential nominations, it has become essential for a candidate to perform well early in the primary and caucus season, weighing in with an early victory or, what is probably more important, an unexpectedly strong early showing. Toward that end, serious presidential aspirants now gear up their campaigns years in advance of the first primaries and caucuses, in the belief that in order to stand any chance of being nominated, they must establish from the very outset the viability of their candidacy. Since nomination contests are, in effect, winnowing processes (see, e.g., Matthews, 1978), presidential aspirants who fail to establish their credibility very early in the race may find themselves left at the post, their supporters having forsaken them for other, seemingly more electable candidates. On the other hand, those who do well early in the fray live to fight another day. Indeed, they are likely, according to a related bit of conventional wisdom, to hop aboard a victory bandwagon, with impressive early performances enhancing their support and this increased support in turn bolstering their subsequent performance.

Taken in tandem, the ideas that it is vital to do well early and that doing well becomes self-perpetuating form the keystones of momentum-based interpretations of the presidential nomination process.