Many pollsters rely, in some way, on past vote history to conduct their surveys. Some pollsters use it to define which voters could be selected to participate in a survey, like a recent Monmouth University poll that selected registered Democrats or independents who turned out in 2018 or in a recent primary, or who registered since 2018. A Neighborhood Research and Media poll was even more limited in its model for who was likely to vote: voters who turned out in either the 2016 or 2018 primary. These polls in Iowa showed Biden with the lead, and the Times/Siena poll also found Biden tied or ahead among these groups.