[justlurking]

The poll isn't oversampling democrats. Check out the last two elections - more democrats turned out to vote than republicans. There have always been more democrats then republicans in this country.

Do you mean Presidential elections? Or, are you including off-year elections?

In 2006 and 2008, there were more Democrats.
In 2004 and 2010, party affiliation was equal.

But, in 2006 was the last off-year election while Bush was President, and opposition to the Iraq war finally came to a head. And, 2008 was the year Obama was elected.

I couldn't find more recent results for 2012 and 2014, but I would expect similar results: In 2012, there were probably more Democrats, and in 2014 it was probably about even.

Overall, there tends to be more Democrats in Presidential elections than there are in off-year elections. But, the "enthusiasm" factor benefited Obama -- along with the mediocre Republican candidates.

This year, I think Trump will be the net beneficiary of enthusiasm -- if for no other reason than because some Republicans will vote for the first time since Reagan. The "woman" factor will help Clinton, but not enough to offset the "disgust" factor.

I think the poll should still be oversampling Democrats, but +8 is unreasonable.

[GonzoII]

If the +60% Republican and -30% Dem turnout in the primaries is paralleled in the General it will be interesting on election night.

[justlurking]

I couldn't find more recent results for 2012 and 2014, but I would expect similar results: In 2012, there were probably more Democrats, and in 2014 it was probably about even.

I found 2012: As expected, it was D+6: 38/32/29 -- almost exactly the same as 2008.

And in 2014, it was R+1: 35/36/28 -- in exit polls conducted for House races.

So, the question remains: given the dynamics of voter enthusiasm, is oversampling that exceeds the difference observed in Obama's first election the correct value to use for this election?

I found this resource for Presidental election:

http://ropercenter.cornell.edu/polls/us-elections/presidential-elections/2012-presidential-election/

On the right side, you can choose Presidential elections back to 1976. Click on the link labelled {year} Group Voting, and then scroll to the bottom. You'll find a category for Party Identification, and the first column of numbers is the total for that party.

An interesting piece of data: in 1984 it was D+3: 38/35/26, but Reagan nearly swept the Electoral College. It was also D+3 in 2000, when it came down to one state (Florida) in the Electoral College.

[Dave W]

Another point - when they take a poll, they use the percentage of people who self identify to a specific party. If they randomly call 800 voters, if 8% self identify as more democrats then that is the percent that is used.

Presidential elections always have more democrats voting because many blacks and Hispanics don't vote in off year elections. 2012 was the first year that blacks voted in a greater percentage than whites.

The other thing is that polls are as of today. A poll today is not necessarily reflective of November, it is if the election is held today. I have to assume that the democrat +8 percent will vary. If it is a bad election for the democrats, their turnout will be depressed and republicans could very well be competitive in turnout.