I want to do some research concerning the historic accuracy of presidential election polling. Is there anywhere I can find a database containing historic polling data from multiple pollsters? FiveThirtyEight makes available a spreadsheet of the polls they have tracked for 2016 and 2020. Is there anything similar to this for previous election cycles? Nate Silver (of FiveThirtyEight) mentions in his methodology for the 2016 model that "Our probabilities are based on the historical accuracy of election polls since 1972." I want to be able to look at that polling data if it exists somewhere.