Take a look at the documented bias in some exit polling data:

“In The 32 States With Exit Poll Estimates For Both A Presidential Race And A Senate Race The Average Error On The Difference Between The Top Two Candidates Was 5.0 Points In The Democratic Direction For President And 3.6 Points In The Democratic Direction For Senate.” (Edison Media Research And Mitofsky International, “Evaluation Of Edison/Mitofsky Election System 2004 For The National Election Pool,” 1/19/05, p. 20)

  • Iowa: NEP Projected Sen. Kerry Winning By 1% – President Bush Carried Iowa By .7%;
  • Nevada: NEP Projected Sen. Kerry Winning By 1.4% – President Bush Carried Nevada By 2.6%;
  • New Mexico: NEP Projected Sen. Kerry Winning By 4.2%- President Bush Carried New Mexico By .8%;
  • Ohio: NEP Projected Sen. Kerry Winning By 6.5% – President Bush Carried By 2.1%;
  • Virginia: NEP Projected Sen. Kerry Winning By 0.5% – President Bush Carried Virginia By 8.2%.   

And some comments: 

Zogby International’s John Zogby: “I’m not sure that I will ever believe an exit poll again … How could they have been so way off? They were worse than virtually every pre-election poll.” (John Cook, “Early Exit Polls Overstated Kerry Results, Media Group Says,” Chicago Tribune, 1/20/05 

Zogby: “The sum total of what we got today is enough to suggest that there should never be exit polls again.” (Donald Lambro, “Polling Firms Blame Youth, Leaks For Errors,” The Washington Times, 1/20/05)

CNN’s Bill Schneider: “The lesson here is put not your faith in exit polls … particularly if the exit poll is close … Exit polls are designed for analysis. … They are not very good …” (William Douglas, “Turnout: The Early Exit Polls Mostly Wrong,” Detroit Free Press, 11/4/04) 

Then-CNN Anchor Judy Woodruff: “People want to jump on (exit polls) because they are the first little sliver, little shred of evidence … It’s dangerous to seize on those numbers and assume anything – and yet that’s what happened.” (Michelle Mittelstadt, “Exit Poll Group Assailed For Erroneous Early Results,” The Dallas Morning News, 11/4/04)