CNN's primetime ratings surge, but for how long?

CNN's beleaguered primetime is doing something unexpected: climbing in the ratings.

Over the past few days, on several occasions, the Time Warner-owned cable-news outlet has trumped its rivals among viewers between the ages of 25 and 54, the demographic most coveted by advertisers. To be certain, Fox News Channel remains the most-watched cable-news network, but CNN is enjoying an uptick.

For two nights, CNN's "Anderson Cooper 360" has won more viewers in the 25-to-54 demo than Fox News' "The O'Reilly Factor," according to data from Nielsen. On Thursday, Cooper attracted an average of 454,000 viewers in the demo compared to O'Reilly's 429,000, according to Nielsen. On Wednesday, Cooper won an average of 431,000 viewers in the demo, Nielsen said, compared to O'Reilly's 386,000.

On Thursday, "Erin Burnett Outfront" at 7 p.m. on CNN notched more 25-to-54 viewers than Greta van Susteren on Fox News at the same hour. And "Piers Morgan Tonight," the 9 p.m. program that CNN has already said will be canceled imminently, won more viewers in the demo than Megyn Kelly did on Fox News at the same hour. Fox News triumphed handily over CNN's second week of "Chicagoland" at 10 p.m., but CNN's lineup from 7 p.m. to 11 p.m. also beat MSNBC's in the demo in every hour last night (MSNBC had more total viewers at 10 p.m. than "Chicagoland").

CNN's victory is a partial one at best. Fox News Channel won primetime overall on Tuesday, Wednesday and Thursday, according to Nielsen, with its 8 p.m. to 11 p.m. lineup averaging more in total viewers and viewers between 25 and 54 than either CNN or MSNBC. And MSNBC's primetime lineup averaged more viewers overall than CNN's on Tuesday and Wednesday.

The question will be whether CNN's results are being boosted for the short term by breaking-news coverage of the recent disappearance of Malaysia Airlines Flight MH370, or if CNN's recent focus on primetime documentaries is gaining traction.

Like a broadcast network showing the finale of a beloved series or the annual Super Bowl, CNN's audience tends to swell during breaking-news moments that grip a good part of the nation. But the network has not been able to keep those viewers once the noise around recent big stories has died down.

CNN's New Primetime Faces?" href="http://variety.com/2014/tv/news/lawyers-lemon-and-real-life-are-these-some-of-cnns-new-primetime-faces-1201127868/" target="_blank" rel="nofollow"> CNN is in the midst of a weeks-long experimental effort in primetime, testing a legal-issues program, a new spotlight on weekend primetime anchor Don Lemon, and more hours of a group of documentaries and docu-series it has commissioned or acquired.

Some of those series have performed well. The Sunday premiere of "CNN Orignal Series: Death Row Stories" won more viewers in the 25-to-54 age range in the 9 p.m. hour than Fox News and MSNBC combined, though, again, Fox News had more viewers in that hour overall.

On Tuesday, "Weed 2: Cannibis Madness," a special report led by Dr. Sanjay Gupta at 10 p.m.,notched 354,000 viewers between 25 and 54, and 144,000 viewers between 18 and 34 - more in both categories than either Fox News Channel or MSNBC. That marked the first time CNN has notched more than 300,000 people in the 25-to-54 demo since an episode of the docuseries "The Sixties" aired January 30th. Fox News still had more viewers overall during that hour.

Others have not performed as robustly. "Chicagoland," a heavily promoted series Allstate's CEO Will Promote New CNN Series 'Chicagoland'" href="http://variety.com/2014/tv/news/in-ad-pact-allstates-ceo-will-promote-new-cnn-series-chicagoland-1201124349/" target="_blank" rel="nofollow">that won ad support from Allstate, has come in second to Fox News Channel Thursdays at 10 p.m. in both overall viewers and viewers between 25-and-54 for both its weeks on the air. And while it has won more viewers in the demo than MSNBC on both weeks, MSNBC had more viewers overall.