Respondents were asked, "Do you support or oppose requiring criminal and mental health background checks on all gun purchases in the United States, including at gun shows and for private sales?" 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.

Respondents were asked, "Do you support or oppose requiring criminal and mental health background checks on all gun purchases in the United States, including at gun shows and for private sales?" Party identification is calculated according to the PID7 variable, a seven point scale of party identification.

Respondents were asked, "Do you support or oppose requiring criminal and mental health background checks on all gun purchases in the United States, including at gun shows and for private sales?" The ideology measure is based on respondent self-placement in response to the following question: "On a scale from 1 to 7, where 1 is extremely liberal, 7 is extremely conservative, and 4 is exactly in the middle, where would you place yourself?" The placements are further classified such that 1 is extremely liberal, 2 is very liberal, 3 is somewhat liberal, 4 is moderate, 5 is somewhat conservative, 6 is very conservative, and 7 is extremely conservative.

Respondents were asked, "Do you support or oppose requiring criminal and mental health background checks on all gun purchases in the United States, including at gun shows and for private sales?" Tea Party identification is based on the following question, also asked in the survey: "Suppose the Tea Party movement organized itself as a political party. When thinking about the next election for Congress, would you vote for the Republican candidate from your district, the Democratic candidate from your district, or the Tea Party candidate from your district?" Those who responded "Republican candidate" are considered Republicans (non-Tea Party movement) and those who responded "Tea Party candidate" are considered Tea Party Republicans.

Respondents were asked, "Do you support or oppose requiring criminal and mental health background checks on all gun purchases in the United States, including at gun shows and for private sales?" Gender is calculated according to the GENDER variable.

Respondents were asked, "Do you support or oppose requiring criminal and mental health background checks on all gun purchases in the United States, including at gun shows and for private sales?" Education is calculated according to the EDUC variable.