Guy Molyneux points out why Bush’s percentage of support in presidential polls may be more important than his lead (if any) over Kerry:
Almost all poll reporting focuses on the “spread,” that is, the difference in the percentage supporting Bush and John Kerry. If we take an average of the most recent ABC/Washington Post, CBS/New York Times, and NBC/Wall Street Journal surveys, it shows Bush with 49 percent and Kerry with 44 percent among registered voters. Such survey results are invariably reduced to the shorthand “Bush up 5,” which sounds like a comfortable lead.
However, in incumbent elections, the incumbent’s percentage of the vote is a far better indicator of the state of the race than the spread. In fact, the percentage of the vote an incumbent president receives in surveys is an extraordinarily accurate predictor of the percentage he will receive on election day — even though the survey results also include a pool of undecided voters. Hence the 50-percent rule: An incumbent who fails to poll above 50 percent is in grave jeopardy of losing his job.
Why 50%? Because an incumbent tends to get what he polled, while the challenger generally picks up a few points:
There have been four incumbent presidential elections in the past quarter-century. If we take an average of the final surveys conducted by the three major networks and their partners, we find that in three of these the incumbent fell short of or merely matched his final poll number, while exceeding it only once, and then by just a single point (Ronald Reagan). On average, the incumbent comes in half a point below his final poll result.
The numbers for challengers look quite different. In every case, the challenger(s) — I include Ross Perot in 1992 and 1996 — exceed their final poll result by at least 2 points, and the average gain is 4 points. In 1980, Ronald Reagan received 51 percent, fully 6 percentage points above his final poll results.
The latest Gallup poll has Bush at 48%; Zogby has Bush at 44%. Unless the race shifts, things aren’t looking good for the incumbent.