It’s really just a matter of there being more democrats than republicans in the US. Natural proportion has to be factored in.
“Newcomers to polling sometimes assume that if you are asking Americans questions about politics, it’s only fair to include an equal number of Republicans and Democrats. While this notion makes some sense on the surface, it’s based on a misunderstanding of what polling is intended to do. The goal of a national political survey isn’t to artificially even the playing field. It’s to represent groups in their actual proportions within the country. And a wide range of evidence shows that there are more Democrats than Republicans in the United States today.”
“Gold-standard, nonpartisan surveys have found for decades that more U.S. adults identify with or lean toward the Democratic Party than the Republican Party – whether these surveys take place under GOP or Democratic presidential administrations. That is the finding of two of the highest-quality surveys that use nationally representative data collected through in-person interviews: the General Social Survey and the American National Election Studies. It’s also the result obtained by numerous other reputable surveys that poll Americans by telephone or online using randomly selected samples of adults, including those done by us here at Pew Research Center, as well as those done by Gallup, Fox News, Kaiser Family Foundation and The Associated Press-NORC. (The Census Bureau, which runs the nation’s most authoritative surveys, notably does not ask Americans about their partisan affiliation.)”
“Newcomers to polling sometimes assume that if you are asking Americans questions about politics, it’s only fair to include an equal number of Republicans and Democrats. While this notion makes some sense on the surface, it’s based on a misunderstanding of what polling is intended to do. The goal of a national political survey isn’t to artificially even the playing field. It’s to represent groups in their actual proportions within the country. And a wide range of evidence shows that there are more Democrats than Republicans in the United States today.”
“Gold-standard, nonpartisan surveys have found for decades that more U.S. adults identify with or lean toward the Democratic Party than the Republican Party – whether these surveys take place under GOP or Democratic presidential administrations. That is the finding of two of the highest-quality surveys that use nationally representative data collected through in-person interviews: the General Social Survey and the American National Election Studies. It’s also the result obtained by numerous other reputable surveys that poll Americans by telephone or online using randomly selected samples of adults, including those done by us here at Pew Research Center, as well as those done by Gallup, Fox News, Kaiser Family Foundation and The Associated Press-NORC. (The Census Bureau, which runs the nation’s most authoritative surveys, notably does not ask Americans about their partisan affiliation.)”
Why public opinion polls don’t include the same number of Republicans and Democrats
While the notion that polls should include an equal number of Republicans and Democrats makes some sense, it’s based on a misunderstanding of what polling is intended to do.
www.pewresearch.org