Bush Literally Phoning It In
Olbermann noted that W is the first sitting president not to attend his party's convention "in several decades," so of course I need to answer the trivia question. It was LBJ in `68. The Secret Sevice advised him not to attend -- good advice as it turned out.
Before that it would have been FDR in 1944, and much before that it was considered bad form to attend.