Last night's Democratic Debate in South Carolina on CNN (from 8pm-10:05pmET) was the No. 1 most-watched primary debate in cable news history among total viewers and all key demos.

The debate averaged 4.9 million Total Viewers and nearly 2 million in A25-54. This is according to Nielsen Fast Nationals (Live + SD).

>More: Click here to download CNN's debate ranker. It includes the top debates going back to 1996.