The basic premise of the unskewers is wrong. Most pollsters don’t weight their results by party self-identification, which polls get by asking a question like “generally speaking, do you usually think of yourself as a….” Party identification is an attitude, not a demographic. There isn’t some national number from the government that tells us how many Democrats and Republicans there are in the country. Some states collect party registration data, but many states do not. Moreover, party registration is not the same thing as party identification. In a state like Kentucky, for example, there are a lot more registered Democrats than registered Republicans, but more voters identified as Republican in the 2014 election exit polls.

A person’s party identification can shift, and therefore the overall balance between parties does too. Democrats have typically had an advantage in self-identification — a 4 percentage point edge in 2000, a 7-point advantage in 2008 and a 6-point edge in 2012, according to exit polls — but they had no advantage in the 2004 election. Since 1952, however, almost every presidential election has featured a Democratic advantage in party identification.