When MSNBC added Tucker Carlson to its prime-time lineup two years ago, the network appeared anxious to capitalize on Fox News’ success as a Republican network. If cable-news viewers were flocking to a conservative, partisan network, MSNBC seemed to believe, then the answer was to keep up by putting more conservatives on the air.

The result Fox News-lite — featuring a lineup with conservative Carlson, conservative Joe Scarborough, and the politically baffling Chris Matthews.

Viewers didn’t exactly flock to this lineup. There’s already a Republican news network; no one needed a pale imitation. But with Keith Olbermann’s ratings continuing to blossom, MSNBC seems to have come to a realization: maybe there’s an audience for those who aren’t sympathetic to the Republican agenda.

Riding a ratings wave from “Countdown With Keith Olbermann,” a program that takes strong issue with the Bush administration, MSNBC is increasingly seeking to showcase its nighttime lineup as a welcome haven for viewers of a similar mind.

Lest there be any doubt that the cable channel believes there is ratings gold in shows that criticize the administration with the same vigor with which Fox News’s hosts often champion it, two NBC executives acknowledged yesterday that they were talking to Rosie O’Donnell about a prime-time show on MSNBC.

And what about self-described “right-winger” Tucker Carlson? An NBC executive told the NYT he’s “in real danger of being canceled.”

On a related note, there's plenty of good discussion out there about whether O'Donnell is a good choice for the MSNBC prime-time lineup.