The ratings results for the month of September show that CNN, long relegated to third place in the prime-time cable news competition, is edging its way back up, while MSNBC is moving in the other direction.
For the month, CNN averaged 257,000 viewers in prime time in the category that counts most to the networks — viewers between the ages of 25 and 54 — because that is where the advertising money goes for news programming. MSNBC was just barely ahead with 269,000 viewers. (Neither approached the leader, Fox News, with 526,000).
Both CNN and MSNBC had one especially strong night because of the Republican presidential debates. With those excluded, however, CNN beat MSNBC, 219,000 to 207,000. A year ago, when Mr. Olbermann still occupied the 8 p.m. hour, MSNBC edged CNN by 83,000 viewers, with 256,000 viewers for MSNBC to 173,000 for CNN.
The change in the September ratings was most noticeable at 8 p.m., where CNN has moved its best-known host, Anderson Cooper. The network’s performance during that hour has improved by 38 percent over last year, growing to 215,000 viewers from 156,000.
On MSNBC, meanwhile, Lawrence O’Donnell has lost 100,000 viewers from the numbers Mr. Olbermann posted last September, with 185,000 viewers in the 25-to-54 age group, a drop of 35 percent. (Bill O’Reilly on Fox, as always, dwarfs his competitors with about three times as many viewers, 611,000.)
More ominously, the falloff for Mr. O’Donnell seems to be affecting MSNBC’s biggest name, Rachel Maddow. Her audience dropped 15 percent this year, to 245,000 from 289,000. She still beats Piers Morgan on CNN in the 9 p.m. hour, but his show has improved 18 percent over Larry King’s ratings last year, with 193,000 viewers to Mr. King’s 164,000.
MSNBC executives endured a contentious parting with Mr. Olbermann last January. Phil Griffin, the president of MSNBC, had a succinct answer to the question of whether the network is feeling the impact of Mr. Olbermann’s departure: “No.”
He added, “I’m confident that we will increase our ratings as politics become the dominant story over the next year.”
Mr. Olbermann is now on the air head-to-head against Mr. O’Donnell. The channel he appears on, Current TV, is not in the league of either CNN or MSNBC in terms of national profile, and his audience totals do not approach any of the other 8 p.m. competitors.
Mr. Olbermann averaged just over 50,000 viewers in the 25-to-54 measure in September, or less than 20 percent of what he attracted on MSNBC. Still, many of those 50,000 may have previously been viewers of MSNBC — and Mr. O’Donnell was 30,000 viewers behind Mr. Cooper in September.
Some industry analysts said the loss of viewers for MSNBC may have to do with strategic changes the network made in recent years.
“MSNBC may be rediscovering the downside of partisan news,” said Chris Daly, a professor of journalism at Boston University. “That is, the size of your audience is essentially cajoled by the size of the electorate that already agrees with you.”
Mr. Cooper is being compared at 8 p.m. against what was hardly a powerhouse CNN entry last year — “Rick’s List,” which featured Rick Sanchez, who was subsequently fired. But Mr. Cooper’s move to 8, which was questioned by some critics, seems to be paying off for CNN. He has made the network much more competitive in that time slot while not losing any momentum for the second show he hosts at 10 p.m.
Ken Jautz, the head of CNN’s domestic news operation, said the network had “been making changes to several hours of our programming in order to grow CNN’s audience during both breaking news and nonbreaking news periods. The fact that our prime-time audience increased this month by 49 percent is certainly gratifying.”
The replay of “Anderson Cooper 360,” which includes news updates but mostly material from the 8 p.m. show, remains CNN’s strongest hour, with 274,000 viewers, well ahead of “The Ed Show” on MSNBC with 200,000 (though both also are well behind Greta Van Susteren on Fox, who had 415,000.)