Rasmussen puts Pat Toomey ahead by four, whether his opponent is Arlen Specter or Joe Sestak. The pollster puts Specter ahead by 13 in the Democratic primary.

The favorable/unfavorable split is interesting, too:

Favorable / Unfavorable
Arlen Specter (D): 44 / 50 (chart)
Pat Toomey (R): 51 / 29
Joe Sestak (D): 36 / 38