"You want to see what a halo effect looks like? Take a look at last year," said Carton, pointing out the Mac's 6.5-point jump in the planned purchase share last summer, immediately after the first-generation iPhone debuted.
That halo effect continues, Carton said. In the August survey, 17 percent of those polled said that they were more likely to buy a Mac desktop or laptop because of the iPhone 3G, the model Apple launched last month.
"This year's halo isn't to the degree of last year's, but in this economic environment and the fact that Apple's hitting its biggest numbers ever, means it's enough to see Apple significantly outperform expectations going forward," said Carton.
"Everything else equal, Apple's outperforming in an incredibly difficult consumer spending environment," Carton observed.
During Apple's most recent quarter, which ended June 30, the company sold a record 2.5 million Macs.