No indications of any “hikes along the Appalachian trail,” my guess is that he is just sick and tired of an increasingly racist and anti-Hispanic GOP, and wants out.

It may also be that he does not want to be in the position of ,making the swing vote for cloture on healthcare reform, and you still need 60 votes even if he is gone (it rounds up).

Charlie Crist, who is running to replace him in 2010 (he had announced that he would not seek reelection) would appoint his successor, but has promised that he will nto appoint himself, so the dynamics are interesting.