Stan­ford Busi­ness School pro­fess­or Jonath­an Bendor de­scribed the “mo­mentum” phe­nomen­on in a 2011 book he coau­thored, A Be­ha­vi­or­al The­ory of Elec­tions. Bendor said what primary voters do ac­tu­ally makes sense, from the point of view of those who want to make a sound choice but haven’t spent much time study­ing their op­tions.

He com­pared it to a diner un­fa­mil­i­ar with Mo­roc­can cuisine go­ing to a Mo­roc­can res­taur­ant for the first time. Look­ing for nat­ive Mo­roc­cans at oth­er tables and or­der­ing what they’re or­der­ing is a sound strategy. Just so, voters in Geor­gia or Vir­gin­ia or Flor­ida look to see what voters did earli­er in Iowa and New Hamp­shire and South Car­o­lina, Bendor said.

“People take cues from oth­er people,” Bendor said. “You shouldn’t think of this as simple-minded con­form­ity. … Vot­ing is an epis­od­ic activ­ity at which most of us are am­a­teurs.”

Ex­amples abound in re­cent pres­id­en­tial elec­tions.