The lack of change in the composition of the electorate in recent years is not unexpected, given that there are limits on how great a share of the electorate a subgroup can represent — mainly its share of the overall U.S. adult population. For example, if 12% of all Americans are black, turnout among blacks would have to be proportionately greater than that of other racial groups for their share of the electorate to exceed 12%. The fact that 11% of likely voters this year are black indicates that turnout among blacks may be slightly less than among other racial groups.

To the extent the electorate looks different now compared with 2004 or 2008, those changes may have as much to do with changes in the larger national adult population as with differential turnout by group this year.

For example, the largest changes in the composition of the electorate compared with the last presidential election concern the partisan affiliation of voters. Currently, 46% of likely voters identify as Democrats or lean Democratic, compared with 54% in 2008. But in 2008, Democrats enjoyed a wide 12-point advantage in party affiliation among national adults, the largest Gallup had seen in at least two decades. More recently, Americans have been about as likely to identify as or lean Republican as to identify as or lean Democratic. Consequently, the electorate has also become less Democratic and more Republican in its political orientation than in 2008. In fact, the party composition of the electorate this year looks more similar to the electorate in 2004 than 2008.