Al-Jazeera has broadcast a video featuring Osama bin-Laden, in which he threatens to repeat the attacks of September 11th and says that the security of the US people depends on US policy - not on who their president is. From the BBC report, he seems to mention Kerry by name, which suggests that he's a) still alive (or was three or four months ago), and b) not in CIA custody. Which I guess means that Bush won't be pulling him out of a sack tomorrow, as people half-expected.
As for what this means for US politics, god only knows. It's a powerful reminder that Bush has utterly failed in the chief objective of the war on terror: capturing bin-Laden (who he once famously called "irrelevant"). And OTOH, there are plenty of Americans stupid enough to say "who cares about Osama? We got Saddam!", or who will rally behind the President in the face of this "new" threat (which is really the old threat that Bush just let lie around for three years).