The one in eight figure would appear to correspond to the bottom graph on the first page of the online article. Of 38% who thought US forces should be decreased, 13% favored immediate withdrawal.
See the reply to Q. 13/14 NET at:
www.washingtonpost.com/wp-srv/politics/polls/postpoll062705.pdf

As to the 58% figure. In politics, that's a landslide.