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A common pastime of poll pundits and readers is analyzing the partisan makeup of respondents to a particular poll and how the opinions of each partisan group are moving and changing. Often lost within this analysis is the fact that there are two different ways of discussing partisanship.

  1. Party ID is determined by how a voter answers a question about which party the voter feels more aligned with. This question usually reads something like this. “Generally speaking, do you usually consider yourself a Democrat, a Republican, an Independent, or something else?” Changing your Party ID is simply a matter of answering the question differently when the next pollster calls.
  2. Party registration in Massachusetts is a demographic fact about a voter, determined by how the voter filled out their registration card. Changing party registration in Massachusetts requires obtaining, filling out, and mailing in a new voter registration card. Not every state has party registration, which is why many national polls and polls conducted in other states often make no reference at all to party registration.

Comparing party registration in Massachusetts with party ID shows that, while overlap between party registration and party ID is considerable, it is not close to perfect. To illustrate this fact, we examine data from an October poll we conducted for WBUR using a list of registered Massachusetts voters (see table). Each of these voters have their party registration indicated in the sample file used for the poll, so we knew whether the interviewee was registered as a Democrat, Republican, another party, or was unenrolled in any party. We then asked each our standard Party ID question, shown above. Comparing the two yields the following chart.

OVERALL

PARTY REGISTRATION

Overall

Democrat

Republican

Unenrolled / Other

Generally speaking, do you usually consider yourself a Democrat, a Republican, an Independent, or something else? Democrat

36%

80%

1%

13%

Republican

15%

4%

76%

8%

Independent

46%

15%

16%

75%

Something Else

2%

1%

6%

3%

Don’t Know / Refused

1%

1%

0%

1%

As shown in the table, between 20% and 24% of each party group members do not identify as a member of that party. Registered Democrats and Republicans are more likely to identify as Independents than as members of the other party. With this distinction in mind, how to compare different polls when one uses party registration and one uses party ID? Poll comparison is inevitable and grew into something of a national sport this year as Election Day approached. When comparing partisan makeup/opinion between different polls though, simply recognize which polls use party ID and which use party registration. This should be easily identifiable by reading the topline or crosstabs provided with the poll release. Recognize that a divergence in the opinion of “Democrats” between two polls may be an artifact of which form of partisanship is included in the poll. As shown here, they are not the same thing.