How does The Daily Show find clips that match content?

For example, The Daily Show will do a piece about newscasters using a term to describe a current event, and include a bunch of clips from various sources where all the newscasters use that term. Or, as they did recently, show clips of televised speeches by Bush and Obama where each used similar phrases several times in the speech. They do it so quickly (daily) and so exhaustively that it makes one wonder if there is a single search engine that has transcripts of every news and CSPAN broadcast, tied to the timecode of the video clips.