Preliminary exit polls vs. Recorded Votes: 1988-2004
Notice the 2004 trend reversal.
Any relation to the new touchscreens with no verified paper ballot?
Deviation Trends: Preliminary Exit Poll to Final Vote

Surprise: Preliminary Exit Poll was right on for Gore in 2000
Democratic Deviations from Preliminary Exit Poll to Final Vote

No Surprise: Repubs always gain in the vote; Dems always lose.
Republican Deviations from Preliminary Exit Poll to Final Vote

Prelim Exit Poll Final Vote Deviation
Year Dem Rep Dem Rep Dem Rep
1988 50.3 49.7 46 54 -4.3 4.3
1992 46 33.2 43 38 -3 4.8
1996 52.2 37.5 49 41 -3.2 3.5
2000 48.5 46.2 48.4 47.9 -0.1 1.7
2004 50.74 47.93 48.28 50.73 -2.46 2.8
Avg 49.55 42.91 46.94 46.33 -2.61 3.42