Consumers seem to have held back on spending in the third quarter from second-quarter levels, but they could snap back in the fourth quarter, based on high confidence levels and falling gasoline prices. Third-quarter GDP is released at 8:30 a.m. EDT Thursday, and the first reading is expected to show growth of 3.2 percent, according to the CNBC/Moody's Analytics rapid update of economists' estimates. "This is likely to have slower consumer spending in it. Generally, you want to have GDP with business investment and spending and I think investment is alright, at least investment in equipment. I think the consumer is a little softer, at about 2 percent," said Chris Rupkey, chief financial economist at Bank of Tokyo-Mitsubishi. In the second quarter, consumer expenditures were at 2.5 percent, while GDP grew at an annualized rate of 4.6 percent. Barclays chief U.S. economist Dean Maki said he expects GDP growth of 3 percent for the third quarter and a weaker contribution from consumer expenditures with a 1.5 percent gain.



A shopper looks at Michael Kors handbags at Macy's flagship store in New York. Scott Mlyn | CNBC

Real consumer spending growth averaged 2.1 percent over the 12 quarters, ending in 2013 and averaged 1.9 percent in the first half of the year, after a weather-related slump in the first quarter, according to Amherst Pierpont chief economist Stephen Stanley. He said a solid gain in June had made it seem the third quarter would be stronger, but consumer demand has instead been more mediocre in recent months.

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But falling gasoline and an improving job market could change that. Both Maki and Rupkey expect a consumer rebound in the fourth quarter, just in time for the holiday shopping season. "I think car sales will snap back more, and gasoline prices are good, and there's a lot of people with pay checks out there. There's simply just more consumers out there and two million more jobs this year, and cheaper gas is good," Rupkey said. "Gas prices can be a game changer in terms of their spending." Rupkey said gasoline price increases in the spring and summer sometimes coincide with economic soft patches, and with more U.S. energy production that could change. Gasoline prices have fallen with dropping world oil prices, weaker in large part because growing North American production is keeping the world well supplied at the same time demand growth is sliding. Read MoreR.I.P. QE: Fed shuts off the printing presses

Maki said consumer spending in the current, fourth quarter could rise sharply. "The risk is it goes to 3 to 3.5 percent. Consumer spending is 68 percent of GDP," he said. "To me that's the dominant force in the near term outlook." He said if spending rises that dramatically, fourth quarter GDP could also move up to the 3 to 3.5 percent level. "We haven't changed our forecast for fourth quarter, at 2.5 percent, but I do think risks are growing to the upside. We're expecting a decline in headline CPI inflation on a quarter-on-quarter basis. Anytime, we've seen that in the past, outside of a recession, that's been accompanied by stronger consumer spending growth," said Maki, adding that's only occurred outside of recession three times in the past 25 years. Energy is behind the drop in CPI. When headline CPI declined in the second quarter of 2003, consumer spending jumped 4.5 percent, and it rose 4.1 percent when CPI declined in Q4, 2006. Consumer price inflation also declined in second quarter, 2010, and consumer spending rose by 3.3 percent.

