The Internet Archive just did something awesome: they launched the TV News Archive. You can search the transcripts for US news broadcasts back to 2009 and then bring up clips that match your terms. This might be useful for all sorts of disciplines, such as journalism, communication studies, political science, and public affairs.
To give you a sense of what can be found on the TV News Archive, here are some canned searches you can click on to run:
Video clips can be linked to (example) or embedded.