It is striking to see that MSNBC’s ratings held up as well as they did in the second quarter, given that Mr. Olbermann, who departed MSNBC in January, was the heart and soul of the channel for the better part of a decade.

For the quarter, his replacement at 8 p.m., “The Last Word with Lawrence O’Donnell,” averaged 974,000 viewers, only a small dip from the 1.06 million that Mr. Olbermann’s “Countdown” had averaged in the same quarter last year.

Among viewers ages 25 to 54, the crucial demographic for cable news, Mr. O’Donnell averaged 248,000, while Mr. Olbermann averaged 263,000 in the same period last year.