Just in at a news conference.
He will stay on and finish out his term, and defend his "honor" but he can't do both and run a re-election campaign.
Oh, and he is going to sell his house, which is what originated the scandal and donate a portion of the sale to local charities.
http://www.nctimes.com/articles/2005/07/14/news/breaking/7005133253.txt
Thanks to Josh Marshall at TPM for being the first to note it.
http://www.talkingpointsmemo.com/archives/week_2005_07_10.php#006115