(FORTUNE Magazine) – To the extent we believe anything about politics, it's this: The economy has an overwhelming influence on voters' choices. James Carville summed it up in 1992 with the phrase "It's the economy, stupid." But recently voters have seemingly turned from the Carvillian wisdom. The economy has been slow for nearly a year, but the public isn't doing its usual Washington bashing. Has something fundamental changed?

One thing is sure: The economy isn't in great shape. Real growth in gross domestic product fell to an anemic 1.3% in the first quarter and 0.2% in the second quarter. During similar periods in the past, presidential job-approval ratings sank with the GDP. Ronald Reagan's ratings slipped from the 60s to the 40s during the 1981-82 recession. Gerald Ford's dropped into the 30s in 1974-75.

Yet George W. Bush's popularity has stood up through the current slowdown. His job-performance rating has hovered in the mid-50s, and Congress' approval rating has been stuck near 50%, even as Americans' view of the economy has deteriorated. Last week the Gallup Organization reported that 63% of Americans consider the economy "only fair" or "poor," while 57% approved of Bush's job in office, unchanged from July.

Experts offer various explanations. Mark Mellman, a Democratic pollster, suggests that "the economic slowdown has not hit average people in a dramatic way." His favorite political divining rod isn't the somewhat amorphous GDP but real per capita disposable personal income. And that has been climbing lately, albeit slowly. Other similar barometers, like consumer spending and overall unemployment, have also held up pretty well.

At the same time, economic conditions often take a while before they translate politically. Karlyn Bowman, the American Enterprise Institute's polling expert, says the public is slow both to acknowledge good economic times and to accept bad ones. "Americans came very late to the view that the economic expansion was real," she notes, "and many of them are still savoring the moment."

Indeed, the last time the U.S. experienced a recession, in 1990-91, voters didn't punish then-President George H.W. Bush until 1992, well after the recovery began. What's more, this year's $38 billion in tax rebates have helped prop up consumer spending and, until recently, consumer confidence.

Then again, something more basic may be under way. Mellman speculates that the electorate may have learned during the past eight years of rapid economic growth that politicians, even if they are President, are only bit players on the financial scene. They deserve neither the blame nor the credit that they usually get for economic performance. "Washington is increasingly irrelevant to everything, including the economy, in the public mind," Mellman says. Which may mean that there's a new conventional wisdom about politics: Focusing on the economy alone is stupid.