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 Republican.
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 Democrats.
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."