Hog,
Results from the 2006 runoff were actually quite closer. It was about 52.6% to 47.4%
http://rangevoting.org/Peru06.html
Here's also an interesting article on this year's election.
http://www.seattlepi.com/business/article/Leftist-leads-in-Peru-election-but-runoff-likely-1329363.php
Of note in that article is the last 2 paragraphs which say: