Responding "don't know" were 7% of Democrats, 9% of independents, and 4% of Republicans.
Measurement of Party ID for this figure is based on two questions. First, respondents were asked whether they consider themselves to be a Democrats, Republicans, independents, other, or not sure. Those who responded that they are independents or "other" were then asked if they lean toward either the Democrats or Republicans. If they indicated that they lean toward one party or the other, they are considered Democrats or Republicans for the purposes of this figure. Only "pure" independents or members of a third party who indicate that they have no preference for Democrats vis-a-vis Republicans are considered independents . Respondents who answered that they are "not sure" for either of the two aforementioned questions are not incorporated into this figure.