I haven't watched much BSG since the first season. Is this something Baltar said at some point?
When you have to explain a joke, it loses so much of its charm. Nevertheless, here goes. (Not spoiled because I assume everyone's seen the second season.)
At the end of the second season, Gaius was (barely) elected President of the Twelve Colonies. This shirt plays on this fact, and American politics; the phrase "Not My President" is commonly interpreted to mean "I didn't vote for George W. Bush."
posted by Antti Helin on September 12 2006, 7:13 pm
This is a COLOSSAL spoiler for season two. It's the only way to get it if you haven't seen season two to the end. Really, DO NOT look if you haven't watched it yet and don't want to be spoiled. Promise me you won't. Even better, promise me you'll go pick up the DVD box right now and watch it.
In the Season 2 finale, despite Roslin's efforts to rig the vote (Adama finds out, roasts her on it with the Edward James Olmos Look and lets democracy have its way), Baltar is elected President of the Colonies in the election that was promised in 'Bastille Day'.
He was elected because Roslin had a freaky religious image (prophecy stuff, banning abortion but for more practical reasons really), and because Baltar promised that he would have the fleet settle down on this miserable but habitable planet they'd found. The slogan itself was originally probably a jab at George W. Bush.