The idea that cable network MSNBC is liberally biased is certainly no stunning revelation. However, when one of its foremost liberal hosts, Keith Olbermann, admits it on the air, that is truly something to behold.

Such actually occurred Thursday evening, and was captured for posterity by Real Clear Politics' Blake Dvorak (h/t NBer SMGalbraith, video available here courtesy Olbermann Watch with thanks to NB reader Damien G.).

To set this up, Democrat presidential candidate John Edwards bought some advertising time on MSNBC Thursday evening to respond to President Bush's address to the nation concerning Iraq. After the ad finished, Olbermann disgracefully said the following: