Casey Building a Lead over Santorum in PA

MyDD has an analysis of the polling in the PA Senate race in 2006 and it doesn't look good for Rick Santorum. Bob Casey has increased his lead over the incumbent in two polls due to a significant drop in Santorum's support:

Trial Heats  Santorum  Casey
Keystone 6/5    37      44
Keystone 3/20   43      44
Q-poll 4/18     35      49
Q-poll 2/14     41      46