It sounds like a riddle of sorts: Is one giant poll of all 50 states the same thing as 50 small polls, one for each state, added together?
If this seems like an odd question, it’s because it hadn’t really come up before this year. CONT.
Nate Silver, FiveThirtyEight
See also: Q: “Is A 50-State Poll As Good As 50 State Polls?” A: Use Mister P. (andrewgelman.com)