(FORTUNE Magazine) – SINCE PETROLEUM BECAME A combustible political issue with the OPEC embargo of 1973, how many incumbent-party presidential candidates have won in the wake of a major oil-price run-up during their party's administration? Zero, it turns out. In 1976, 1980, and 1992, candidates of the incumbent party went down in flames after dramatic price spikes caused economic shocks during the term. In 2000, even though nobody believes rising oil defeated Al Gore, the fact remains that crude prices doubled in the 18 months before the election.

So with crude crossing the $50-a-barrel threshold in late September and continuing to set new records, it raises the question, Will George W. Bush pay for this year's 50%-plus rise in oil?

Most experts argue that crude prices have a significant impact only when oil spikes contribute to a recession, and this time around the recession preceded the big run-up. Yet the Gallup poll's chief economist, Dennis Jacobe, describes energy prices as a "stealth issue." The campaigns may not be focusing on oil or gas prices, but voters, who are reminded of high prices every time they visit the pump, care a lot. As Jacobe puts it, "It's off the radar screen, but it's there."

A late-September UBS/Gallup poll, for instance, detected softness in support for the President in an unexpected quarter: investors. Although a majority still favor Bush (50% to 36%), 37% in the Bush camp and 30% of Kerry supporters say they wouldn't be "upset" if their candidate lost. In Jacobe's view, that's a sign that what should be a solidly pro-Bush group could be swayed. The reason: Investors are worried about the effects of high energy prices and outsourcing, with 56% of respondents citing both as the factors that are hurting the investment climate "a lot."

As always with polling, the answer depends on the question. When voters of any stripe are asked whether high gasoline prices worry them, huge numbers--80% or more--say yes. But when they're asked to list their biggest concerns, only a single-digit group volunteer oil or energy prices (though energy is a likely component for those who name "the economy" as a fear). Whatever the case, while it's unlikely oil will swing the election, this is one issue where incumbency doesn't seem to give Bush an advantage. -- Nicholas Varchaver