While most elections in the United States are simultaneous (with all voters casting their ballots on the same day), there are elections, such as the presidential primary system, in which voters cast their ballots over an extended period of time. Sequential voting poses an interesting puzzle for scholars of voting behavior, particularly given the information flow of elections, but also the strategic considerations of what is effectively an iterated process over time. Presidential primaries are essentially a sequence or series of state party races that begin in early February and last until June of a presidential election year. Although not precisely the same as the presidential primary process, mail-in balloting or early voting, whereby some voters, especially stronger partisans, choose to cast their ballots prior to election day, offers another example of sequential voting in the United States.