In an amazing January 2006 speech to the American Constitution Society, Al Gore gave a passionate defense of the Constitution, and railed against the Bush administration abuses on domestic spying. Keep in mind this was before a lot of the really dirty stuff even came out, with a complicit GOP Congress unwilling to do any oversight of the executive branch. For anyone who thinks Gore would be a single-issue candidate on the environment, should he choose to run, this video is a must-see.
Yes, it is an hour and five minutes long. It's well worth it.