In his syndicated column, political demographer Michael Barone looks at some of the pratfalls of polling. He also makes some important points about how most media polls are overcounting Democrats:
In 2004, the electorate that went to the polls or voted absentee was,
according to the adjusted NEP exit poll, 37 percent Democratic and 37
percent Republican. In party identification, it was the most Republican
electorate since George Gallup conducted his first random sample poll
in October 1935.
But most recent national polls show Democrats with an advantage in
party identification in the vicinity of 5 percent to 12 percent. Party
identification usually changes slowly. Historically, voters have
switched from candidates of one party to candidates of the other more
readily than they have changed their party identification.
Over time, big changes in party ID can and do occur. When I started
in the polling business, in 1974, national party identification was
almost 50 percent Democratic and not much more than 25 percent
Since then, Democratic party ID has fallen, particularly in the
South, where many voters who considered themselves Democrats found
themselves voting Republican for president and, increasingly in the
1980s and 1990s, for other offices, as well.
Republican party ID has increased. But that's a process that took
decades. If you could go back in history and conduct polls, I don't
think you'd find any, and certainly not many, two-year periods when the
balance in party identification shifted from even to having one party
12 percent ahead of the other.
At the end, Barone notes a very interesting little tidbit about how poll interviewers can skew results:
Interviewers can inject bias in the results. The late Warren Mitofsky,
who conducted the 2004 NEP exit poll, went back and found that the
greatest difference between actual results in exit poll precincts and
the reports phoned in to NEP came where the interviewers were female
graduate students -- and almost all the discrepancies favored the
Hat tip: John at Power Line who adds: "Barone doesn't draw this conclusion, but the implication of all of this
is that Democrats shouldn't start popping the champage corks just yet."