Opinion polls are surveys of public opinion obtained from questioning a representative sample of the population. They can give us a sense of which political candidate is likely to win but approach them with caution - polls are not infallible!
Ratings of election pollsters based on analysis by FiveThirtyEight looking at historical accuracy of the polls and polling methodology.
Below is a list of some of the biggest poll sources. (**Note: Some sources will not provide free access to full data.)
If you're looking for historical election statistics, these resources have a range of statistics to explore from the earliest years of American democracy to the 2016 Presidential election.
MIT datalab contains constituency (state-level) returns for elections to the U.S. presidency from 1976 to 2016 and county-level returns for presidential elections from 2000 to 2016.
The University of Richmond's Digital Scholarship Lab has mapped data for Congressional and Presidential elections by state, county and density. Includes accompanying scholarly analysis.
A New Nation Votes is a searchable collection of election returns from the earliest years of American democracy, 1787-1825.
Statistics collected by the US Census Bureau about voting and voter registration. Includes demographic and voter turnout data.