After ticking up slightly earlier this month, the index declined during the past two weeks to its current -33, the lowest level of the year, according to the poll.
During recent weeks, slightly more consumers said they think economic conditions are "getting worse." These expectations for the economy basically match the average for July and are worse than those consumers held at this time a year ago.
But the declines aren't surprising considering the downturn in the stock markets, the lack of job creation and talk of the economic recovery slowing down.
The Gallup index may reflect a decline in the consumer confidence report expected out on Friday, although it could show a modest improvement compared with July.
Regardless, the most troubling aspect of the current economic confidence data is that they show no improvement from a year ago, the Gallup analysis said.
"In fact, Americans are slightly less optimistic about the future direction of the economy today than they were at this time in 2009. This is not good news for retailers or for incumbents facing re-election this November."