NEW YORK (CNN/Money) - Coming off a spectacular Tuesday night premiere, 'American Idol' saw ratings fall during its second night compared to a year ago.

According to Nielsen Media Research data, Wednesday's hour-long 'American Idol' drew 26.7 million viewers, 10 percent fewer than its second-night broadcast a year ago. 'Idol' also attracted fewer young and middle-aged adults, the ones advertisers covet most.

The Fox show had a 27 share in the lucrative category of 18 to 49 year-old viewers, compared to a 32 share the same time a year ago. A share represents the percentage of viewers in a category who are watching television in a given time period.

Fox, a News Corp. (Research) division, should probably blame the ABC hit drama 'Lost' for stealing some of the thunder from 'Idol,' said Brad Adgate, the senior vice president of corporate research at Horizon Media, a New York branding firm.

"The stiffer competition probably played into (the 'Idol' falloff)," said Adgate.

Some 19.7 million viewers tuned into 'Lost,' one of the television season's biggest draws and a major factor behind ABC's long-awaited revival. According to the Walt Disney (Research) network, 'Lost' had its third-best ratings night since its September launch.

Adgate, however, cautioned that it's too soon to say whether the decline in 'Idol' ratings is a bad sign for Fox. Among other things, he noted the talent competition's "incredible" two-hour premiere Tuesday. Its best debut yet in four seasons, 'Idol' ratings were up about 10 percent compared to last year.

"Even though the (Wednesday night) ratings are down versus a year ago, those are really strong numbers," he said. "I think Fox is pretty happy with the two nights."

Indeed, the strength of 'Idol' helped Fox win the ratings war both Tuesday and Wednesday night.

Fox is banking on 'Idol' and its spy drama '24,' which just had its premiere, to pull it out of last place among the Big Four broadcast networks. Analysts are optimistic that the two shows will give the network the lift it needs.