Last night viewers of cable news were the first to learn that Republican Karen Handel had defeated Democrat Jon Ossoff in the special election to fill a U.S. House seat in Georgia. Long before any news outlet formally declared Ms. Handel’s victory, CNN and MSNBC regulars disclosed the outcome with their funereal tones and cheerless visages. It’s becoming a competitive advantage for the two cable nets on election nights, allowing viewers to learn unofficial results with one glance at the screen.

MSNBC’s...