Gallup analysts blame the latest dip in confidence on Washington's debate over government spending. The government could shut down on Oct. 1 without a deal, and Congress faces another deadline in mid-October to raise the debt ceiling.

Unstable unemployment is also a reason for the declining confidence, the Conference Board said Tuesday in a separate report that also covered lower consumer confidence. 

“Consumer confidence decreased in September as concerns about the short-term outlook for both jobs and earnings resurfaced, while expectations for future business conditions were little changed,” said Lynn Franco, director of economic indicators for the group. “Consumers’ assessment of current business and labor market conditions, however, was more positive.” 

Economists frequently track the consumer confidence index because it’s a reliable measure of people’s optimism about the economy. Since the recession hit in 2008, the economy has been struggling, but gradually improving.