The Great Party ID Debate in Polling

Rarely does a poll go by where I or some other blogger doesn’t complain about the inherent built-in inaccuracy of very expensive polling due to the party ID split.  Sometimes the split is purposeful to reflect the most recently identified electorate.  Other times it is an attempt to accurately forecast the upcoming turnout (always a hard task). One of the true experts on this topic takes on this herculean task with his must-read Morning Jay Column.  I’ll excerpt the important point below but if you have the slightest interest in this topic, I strongly encourage you to click through and read the whole thing:

Over the last quarter century, party identification on Election Day has actually been quite stable in presidential elections. On average, Democrats have enjoyed a 3-point advantage going back to 1984; in most elections, the edge falls between D+1 and D+5. Some argue that there is a recent trend that favors the Democrats, as 2008 saw the highest Democratic advantage since 1980. On the other hand, 2004 saw the best Republican year in generations.

A lot of the movement in party identification from cycle to cycle is not the two sides “turning out their bases,” as is commonly assumed. Instead, it has to do with how the marginal partisans on both sides are reacting to the national political climate. Remember: Something like 35 percent of the population calls itself “independent,” but only about 10 percent has no party affiliation whatsoever. That means there are a lot of “hidden” partisans who can “emerge” in good years for their sides. For instance, in a good year for the GOP, regular Republican voters who often think of themselves as independent will call themselves Republicans, and so the percentage of Republicans in the electorate will rise. In a bad year for the GOP, they’ll call themselves independents and the percentage of Republicans will fall. Same goes for the Democrats.

This actually explains much of the Democratic advantage 2008. A 20 percent increase in the black vote relative to 2004 helped boost the Democratic share of the electorate to 39 percent; meanwhile, some Republican voters started calling themselves “independents.” They still voted for McCain, however, which explains why Obama only won the independent vote by 8 points, compared to the 20-point victory House Democrats enjoyed in 2006.

Applying this historical perspective to today’s polls, I think it is unlikely that we are going to see a Democratic advantage equal to or larger than the D+7 Obama enjoyed in 2008. I see something closer to the historical average of D+3. That’s just a guess, albeit it an educated one.

And when I look at partisan splits in the polls, the farther a poll moves away from D+3, the less I am willing to take a “naïve” view of it, i.e. just look at the head-to-head margin. Instead, I look closely at the way the independent vote is leaning, as that is a good gauge of where the race actually stands. As a general rule of thumb, if you see President Obama leading in the overall numbers but losing among independents, it stands to reason that the poll is more Democratic than what we shall see on Election Day.

4 Trackbacks

  1. […] for accuracy sake. In an exhaustive post worth everyone’s read anytime this topic comes up, Jay Cost at the Weekly Standard completely debunked anyone believing the current polling reflects the electorate who will show up […]

  2. […] belief when poll after poll says we are losing, even if ever-so-slightly? Jay Cost smartly made the quantitative case. Today I am going to make the substantive […]

  3. […] issue with this blog.  We blogged a few different thoughts on the debate from the invaluable Jay Cost’s D +3 estimate to The Winston Group’s historical perspective. Chris Palko of Smart Media Group whose awesome […]

  4. […] 9 percentage points greater than Republicans. This blog has hammered the issue of party ID time and again. Basically there is a zero percent change the Democrat’s advantage at the polls in […]

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