Its multipartisan membership consists of political consultants, pollsters, media consultants, campaign managers, corporate public affairs officers, professors, lobbyists, fundraisers, congressional staffers, and vendors.
en.wikipedia.org Hence, a moving average is used to link all polls from all pollsters into one series.
en.wikipedia.org After the 1992 election, most opinion pollsters altered their methodology to try to correct for this observed behaviour of the electorate.
en.wikipedia.org This can be attributed to varying polling methods, demographics, and sample sizes between pollsters, amongst other things.
en.wikipedia.org