Right now CSPAN's coverage of the White House Correspondents' is the camera spanning a bunch of people talking, eating, drinking, looking fabulous. The entire evening, CSPAN has had to cut in to the live camera feed and give limited comments on the menu and other guests invited by the media organizations present.
This has left a major gap for Twitter to provide the continuous commentary we are now used to at awards shows and major live events. CSPAN has been promoting the hashtag #nerdprom on the screen all evening, and attendees and viewers alike have been tweeting away their own commentary. The second-screen phenomenon is clearly alive and well!