Why ask registration? A lot of states don't require you to register with a party to vote in the primary, and some have open primaries, and in places that are one-party-dominated some people register with the dominant party so they can have some voice in picking candidates. As a result, party registration tends to be a much less reliable indicator of partisan preference than the more-standard partisan identification question.
I'm curious to know the rationale behind asking about respondents' registration. Do you have an inkling that registration results are more meaningful than they've been given credit for being?
Don't they have to ask registration to show that the poll is not tilted to dems or reps? If all respondants were from one party the poll numbers would be skewed to the right or left and thus meaningless as far as the whole country goes.
You could acheive the same thing by asking partisan identification -- in fact, that's what most polls do. The reason they don't ask for registration is that the rules of registration vary widely from state to state, so it is not an equally valid measure of partisan loyalties in different parts of the country.
Respondents don't differentiate between their self identification as to party preference and if they actually had to register to vote with a party preference.
Since I've lived in Missouri (a fair amount of time) voters do not register by party - believe me, if we did it'd make organizing and GOTV a hell of a lot easier.
It's almost become a running gag for us when we do voter ID calls. We'll ask the party ID question and the person on the other end of the line with a voter history going back to the beginning of time (or not) will indignantly reply, "Why, I've been a registered XXXXXXXX all my life!" We never bother to reply, "You can't be, voters in Missouri don't register by party" - it'd just piss them off.
