Chevrolet’s all-new Volt extended-range electric vehicle was a boon to the automaker’s image as it emerged from the shadow of “Old GM.” But according to a new report, demand for the car is cooling.

The Volt entered the market at the same time as the Nissan Leaf EV, but it provided a unique alternative to the Leaf’s all-electric powertrain. In lieu of plugging-in after the battery is depleted, owners of the Volt can continue driving since the car’s onboard gasoline engine can also re-charge the battery. This unique system enables 35-miles of emissions-free driving (plus an additional 344 miles under gasoline power) and virtually eliminates the range anxiety associated with traditional all-electric models.

Overall, sales of the Volt and the Leaf have been marginal in comparison to overall auto sales. But while Chevy has sold about 3,200 Volts through the end of July, Nissan has moved 4,500 Leafs.

If you ask CNW Marketing Research, the sales gap between the two models may soon increase. Their new study says potential buyers are quickly losing interest in the Volt. In March, 21% of so-called Early Adapters said they were “very likely” to consider buying a Volt, while 38.1% said they were “likely” to do the same. That slipped to 14.6% saying “very likely” in July, and 31.1% “likely.”

“It’s way too early to tell, but the signs aren’t encouraging,” said CNW’s chief analyst Art Spinella.

According to CNW data, the price of the Volt is one of its biggest weaknesses. The Volt initially carried a price of $41,000, though it qualified for a $7,500 federal tax credit. For 2012, Chevy is dropping the price to $39,995, but that price tag is still higher than the Nissan Leaf and nearly double the price of a comparable fuel-efficient gasoline-powered car.

Despite doubts, GM believes the Volt will be a stellar success. The automaker has already increased production and expects sales to top 40,000 units next year. And, thanks to a new partnership with battery supplier A123, the automaker is preparing to introduce more battery-electric vehicles in 2014.